diff --git a/deltachat-ffi/src/lib.rs b/deltachat-ffi/src/lib.rs
index 3fea176b0..6728c8a2e 100644
--- a/deltachat-ffi/src/lib.rs
+++ b/deltachat-ffi/src/lib.rs
@@ -31,7 +31,7 @@ use rand::Rng;
 
 use deltachat::chat::{ChatId, ChatVisibility, MuteDuration, ProtectionStatus};
 use deltachat::constants::DC_MSG_ID_LAST_SPECIAL;
-use deltachat::contact::{Contact, Origin};
+use deltachat::contact::{Contact, ContactId, Origin};
 use deltachat::context::Context;
 use deltachat::ephemeral::Timer as EphemeralTimer;
 use deltachat::key::DcKey;
@@ -493,14 +493,16 @@ pub unsafe extern "C" fn dc_event_get_data1_int(event: *mut dc_event_t) -> libc:
         | EventType::ChatEphemeralTimerModified { chat_id, .. } => chat_id.to_u32() as libc::c_int,
         EventType::ContactsChanged(id) | EventType::LocationChanged(id) => {
             let id = id.unwrap_or_default();
-            id as libc::c_int
+            id.to_u32() as libc::c_int
         }
         EventType::ConfigureProgress { progress, .. } | EventType::ImexProgress(progress) => {
             *progress as libc::c_int
         }
         EventType::ImexFileWritten(_) => 0,
         EventType::SecurejoinInviterProgress { contact_id, .. }
-        | EventType::SecurejoinJoinerProgress { contact_id, .. } => *contact_id as libc::c_int,
+        | EventType::SecurejoinJoinerProgress { contact_id, .. } => {
+            contact_id.to_u32() as libc::c_int
+        }
         EventType::WebxdcStatusUpdate(msg_id) => msg_id.to_u32() as libc::c_int,
     }
 }
@@ -715,7 +717,11 @@ pub unsafe extern "C" fn dc_get_chatlist(
     let ctx = &*context;
     let qs = to_opt_string_lossy(query_str);
 
-    let qi = if query_id == 0 { None } else { Some(query_id) };
+    let qi = if query_id == 0 {
+        None
+    } else {
+        Some(ContactId::new(query_id))
+    };
 
     block_on(async move {
         match chatlist::Chatlist::try_load(ctx, flags as usize, qs.as_deref(), qi)
@@ -743,7 +749,7 @@ pub unsafe extern "C" fn dc_create_chat_by_contact_id(
     let ctx = &*context;
 
     block_on(async move {
-        ChatId::create_for_contact(ctx, contact_id)
+        ChatId::create_for_contact(ctx, ContactId::new(contact_id))
             .await
             .log_err(ctx, "Failed to create chat from contact_id")
             .map(|id| id.to_u32())
@@ -763,7 +769,7 @@ pub unsafe extern "C" fn dc_get_chat_id_by_contact_id(
     let ctx = &*context;
 
     block_on(async move {
-        ChatId::lookup_by_contact(ctx, contact_id)
+        ChatId::lookup_by_contact(ctx, ContactId::new(contact_id))
             .await
             .log_err(ctx, "Failed to get chat for contact_id")
             .unwrap_or_default() // unwraps the Result
@@ -1340,7 +1346,10 @@ pub unsafe extern "C" fn dc_get_chat_contacts(
         let arr = dc_array_t::from(
             chat::get_chat_contacts(ctx, ChatId::new(chat_id))
                 .await
-                .unwrap_or_log_default(ctx, "Failed get_chat_contacts"),
+                .unwrap_or_log_default(ctx, "Failed get_chat_contacts")
+                .iter()
+                .map(|id| id.to_u32())
+                .collect::<Vec<u32>>(),
         );
         Box::into_raw(Box::new(arr))
     })
@@ -1450,7 +1459,7 @@ pub unsafe extern "C" fn dc_is_contact_in_chat(
     block_on(chat::is_contact_in_chat(
         ctx,
         ChatId::new(chat_id),
-        contact_id,
+        ContactId::new(contact_id),
     ))
     .log_err(ctx, "is_contact_in_chat failed")
     .unwrap_or_default() as libc::c_int
@@ -1471,7 +1480,7 @@ pub unsafe extern "C" fn dc_add_contact_to_chat(
     block_on(chat::add_contact_to_chat(
         ctx,
         ChatId::new(chat_id),
-        contact_id,
+        ContactId::new(contact_id),
     ))
     .log_err(ctx, "Failed to add contact")
     .is_ok() as libc::c_int
@@ -1492,7 +1501,7 @@ pub unsafe extern "C" fn dc_remove_contact_from_chat(
     block_on(chat::remove_contact_from_chat(
         ctx,
         ChatId::new(chat_id),
-        contact_id,
+        ContactId::new(contact_id),
     ))
     .log_err(ctx, "Failed to remove contact")
     .is_ok() as libc::c_int
@@ -1827,7 +1836,8 @@ pub unsafe extern "C" fn dc_lookup_contact_id_by_addr(
         Contact::lookup_id_by_addr(ctx, &to_string_lossy(addr), Origin::IncomingReplyTo)
             .await
             .unwrap_or_log_default(ctx, "failed to lookup id")
-            .unwrap_or(0)
+            .map(|id| id.to_u32())
+            .unwrap_or_default()
     })
 }
 
@@ -1847,6 +1857,7 @@ pub unsafe extern "C" fn dc_create_contact(
     block_on(async move {
         Contact::create(ctx, &name, &to_string_lossy(addr))
             .await
+            .map(|id| id.to_u32())
             .unwrap_or(0)
     })
 }
@@ -1885,7 +1896,9 @@ pub unsafe extern "C" fn dc_get_contacts(
 
     block_on(async move {
         match Contact::get_all(ctx, flags, query).await {
-            Ok(contacts) => Box::into_raw(Box::new(dc_array_t::from(contacts))),
+            Ok(contacts) => Box::into_raw(Box::new(dc_array_t::from(
+                contacts.iter().map(|id| id.to_u32()).collect::<Vec<u32>>(),
+            ))),
             Err(_) => ptr::null_mut(),
         }
     })
@@ -1922,7 +1935,10 @@ pub unsafe extern "C" fn dc_get_blocked_contacts(
             Contact::get_all_blocked(ctx)
                 .await
                 .log_err(ctx, "Can't get blocked contacts")
-                .unwrap_or_default(),
+                .unwrap_or_default()
+                .iter()
+                .map(|id| id.to_u32())
+                .collect::<Vec<u32>>(),
         )))
     })
 }
@@ -1933,18 +1949,18 @@ pub unsafe extern "C" fn dc_block_contact(
     contact_id: u32,
     block: libc::c_int,
 ) {
-    if context.is_null() || contact_id <= constants::DC_CONTACT_ID_LAST_SPECIAL as u32 {
+    if context.is_null() || contact_id <= constants::DC_CONTACT_ID_LAST_SPECIAL.to_u32() {
         eprintln!("ignoring careless call to dc_block_contact()");
         return;
     }
     let ctx = &*context;
     block_on(async move {
         if block == 0 {
-            Contact::unblock(ctx, contact_id)
+            Contact::unblock(ctx, ContactId::new(contact_id))
                 .await
                 .ok_or_log_msg(ctx, "Can't unblock contact");
         } else {
-            Contact::block(ctx, contact_id)
+            Contact::block(ctx, ContactId::new(contact_id))
                 .await
                 .ok_or_log_msg(ctx, "Can't block contact");
         }
@@ -1963,7 +1979,7 @@ pub unsafe extern "C" fn dc_get_contact_encrinfo(
     let ctx = &*context;
 
     block_on(async move {
-        Contact::get_encrinfo(ctx, contact_id)
+        Contact::get_encrinfo(ctx, ContactId::new(contact_id))
             .await
             .map(|s| s.strdup())
             .unwrap_or_else(|e| {
@@ -1978,14 +1994,14 @@ pub unsafe extern "C" fn dc_delete_contact(
     context: *mut dc_context_t,
     contact_id: u32,
 ) -> libc::c_int {
-    if context.is_null() || contact_id <= constants::DC_CONTACT_ID_LAST_SPECIAL as u32 {
+    if context.is_null() || contact_id <= constants::DC_CONTACT_ID_LAST_SPECIAL.to_u32() {
         eprintln!("ignoring careless call to dc_delete_contact()");
         return 0;
     }
     let ctx = &*context;
 
     block_on(async move {
-        match Contact::delete(ctx, contact_id).await {
+        match Contact::delete(ctx, ContactId::new(contact_id)).await {
             Ok(_) => 1,
             Err(_) => 0,
         }
@@ -2004,7 +2020,7 @@ pub unsafe extern "C" fn dc_get_contact(
     let ctx = &*context;
 
     block_on(async move {
-        Contact::get_by_id(ctx, contact_id)
+        Contact::get_by_id(ctx, ContactId::new(contact_id))
             .await
             .map(|contact| Box::into_raw(Box::new(ContactWrapper { context, contact })))
             .unwrap_or_else(|_| ptr::null_mut())
@@ -2427,7 +2443,7 @@ pub unsafe extern "C" fn dc_array_get_contact_id(
         return 0;
     }
 
-    (*array).get_location(index).contact_id
+    (*array).get_location(index).contact_id.to_u32()
 }
 #[no_mangle]
 pub unsafe extern "C" fn dc_array_get_msg_id(
@@ -2943,7 +2959,7 @@ pub unsafe extern "C" fn dc_msg_get_from_id(msg: *mut dc_msg_t) -> u32 {
         return 0;
     }
     let ffi_msg = &*msg;
-    ffi_msg.message.get_from_id()
+    ffi_msg.message.get_from_id().to_u32()
 }
 
 #[no_mangle]
@@ -3654,7 +3670,7 @@ pub unsafe extern "C" fn dc_contact_get_id(contact: *mut dc_contact_t) -> u32 {
         return 0;
     }
     let ffi_contact = &*contact;
-    ffi_contact.contact.get_id()
+    ffi_contact.contact.get_id().to_u32()
 }
 
 #[no_mangle]
diff --git a/deltachat-ffi/src/lot.rs b/deltachat-ffi/src/lot.rs
index 1b64bbd1d..9426ef425 100644
--- a/deltachat-ffi/src/lot.rs
+++ b/deltachat-ffi/src/lot.rs
@@ -111,19 +111,19 @@ impl Lot {
         match self {
             Self::Summary(_) => Default::default(),
             Self::Qr(qr) => match qr {
-                Qr::AskVerifyContact { contact_id, .. } => *contact_id,
+                Qr::AskVerifyContact { contact_id, .. } => contact_id.to_u32(),
                 Qr::AskVerifyGroup { .. } => Default::default(),
-                Qr::FprOk { contact_id } => *contact_id,
-                Qr::FprMismatch { contact_id } => contact_id.unwrap_or_default(),
+                Qr::FprOk { contact_id } => contact_id.to_u32(),
+                Qr::FprMismatch { contact_id } => contact_id.unwrap_or_default().to_u32(),
                 Qr::FprWithoutAddr { .. } => Default::default(),
                 Qr::Account { .. } => Default::default(),
                 Qr::WebrtcInstance { .. } => Default::default(),
-                Qr::Addr { contact_id } => *contact_id,
+                Qr::Addr { contact_id } => contact_id.to_u32(),
                 Qr::Url { .. } => Default::default(),
                 Qr::Text { .. } => Default::default(),
-                Qr::WithdrawVerifyContact { contact_id, .. } => *contact_id,
+                Qr::WithdrawVerifyContact { contact_id, .. } => contact_id.to_u32(),
                 Qr::WithdrawVerifyGroup { .. } => Default::default(),
-                Qr::ReviveVerifyContact { contact_id, .. } => *contact_id,
+                Qr::ReviveVerifyContact { contact_id, .. } => contact_id.to_u32(),
                 Qr::ReviveVerifyGroup { .. } => Default::default(),
             },
             Self::Error(_) => Default::default(),
diff --git a/examples/repl/cmdline.rs b/examples/repl/cmdline.rs
index df86235d1..e44f6d868 100644
--- a/examples/repl/cmdline.rs
+++ b/examples/repl/cmdline.rs
@@ -209,7 +209,7 @@ async fn log_msg(context: &Context, prefix: impl AsRef<str>, msg: &Message) {
         contact_id,
         msgtext.unwrap_or_default(),
         if msg.has_html() { "[HAS-HTML]️" } else { "" },
-        if msg.get_from_id() == 1 {
+        if msg.get_from_id() == DC_CONTACT_ID_SELF {
             ""
         } else if msg.get_state() == MessageState::InSeen {
             "[SEEN]"
@@ -267,7 +267,7 @@ async fn log_msglist(context: &Context, msglist: &[MsgId]) -> Result<()> {
     Ok(())
 }
 
-async fn log_contactlist(context: &Context, contacts: &[u32]) -> Result<()> {
+async fn log_contactlist(context: &Context, contacts: &[ContactId]) -> Result<()> {
     for contact_id in contacts {
         let mut line2 = "".to_string();
         let contact = Contact::get_by_id(context, *contact_id).await?;
@@ -296,7 +296,7 @@ async fn log_contactlist(context: &Context, contacts: &[u32]) -> Result<()> {
         let peerstate = Peerstate::from_addr(context, addr)
             .await
             .expect("peerstate error");
-        if peerstate.is_some() && *contact_id != 1 {
+        if peerstate.is_some() && *contact_id != DC_CONTACT_ID_SELF {
             line2 = format!(
                 ", prefer-encrypt={}",
                 peerstate.as_ref().unwrap().prefer_encrypt
@@ -714,7 +714,7 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
         }
         "createchat" => {
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
-            let contact_id: u32 = arg1.parse()?;
+            let contact_id = ContactId::new(arg1.parse()?);
             let chat_id = ChatId::create_for_contact(&context, contact_id).await?;
 
             println!("Single#{} created successfully.", chat_id,);
@@ -742,7 +742,7 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
             ensure!(sel_chat.is_some(), "No chat selected");
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
 
-            let contact_id_0: u32 = arg1.parse()?;
+            let contact_id_0 = ContactId::new(arg1.parse()?);
             chat::add_contact_to_chat(&context, sel_chat.as_ref().unwrap().get_id(), contact_id_0)
                 .await?;
             println!("Contact added to chat.");
@@ -750,7 +750,7 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
         "removemember" => {
             ensure!(sel_chat.is_some(), "No chat selected.");
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
-            let contact_id_1: u32 = arg1.parse()?;
+            let contact_id_1 = ContactId::new(arg1.parse()?);
             chat::remove_contact_from_chat(
                 &context,
                 sel_chat.as_ref().unwrap().get_id(),
@@ -1134,7 +1134,7 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
         "contactinfo" => {
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
 
-            let contact_id: u32 = arg1.parse()?;
+            let contact_id = ContactId::new(arg1.parse()?);
             let contact = Contact::get_by_id(&context, contact_id).await?;
             let name_n_addr = contact.get_name_n_addr();
 
@@ -1169,16 +1169,16 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
         }
         "delcontact" => {
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
-            Contact::delete(&context, arg1.parse()?).await?;
+            Contact::delete(&context, ContactId::new(arg1.parse()?)).await?;
         }
         "block" => {
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
-            let contact_id = arg1.parse()?;
+            let contact_id = ContactId::new(arg1.parse()?);
             Contact::block(&context, contact_id).await?;
         }
         "unblock" => {
             ensure!(!arg1.is_empty(), "Argument <contact-id> missing.");
-            let contact_id = arg1.parse()?;
+            let contact_id = ContactId::new(arg1.parse()?);
             Contact::unblock(&context, contact_id).await?;
         }
         "listblocked" => {
diff --git a/src/chat.rs b/src/chat.rs
index d92c800f1..5a56fd804 100644
--- a/src/chat.rs
+++ b/src/chat.rs
@@ -20,7 +20,7 @@ use crate::constants::{
     DC_CONTACT_ID_LAST_SPECIAL, DC_CONTACT_ID_SELF, DC_GCM_ADDDAYMARKER, DC_GCM_INFO_ONLY,
     DC_RESEND_USER_AVATAR_DAYS,
 };
-use crate::contact::{addr_cmp, Contact, Origin, VerifiedStatus};
+use crate::contact::{addr_cmp, Contact, ContactId, Origin, VerifiedStatus};
 use crate::context::Context;
 use crate::dc_receive_imf::ReceivedMsg;
 use crate::dc_tools::{
@@ -153,7 +153,10 @@ impl ChatId {
     /// Returns the [`ChatId`] for the 1:1 chat with `contact_id` if it exists.
     ///
     /// If it does not exist, `None` is returned.
-    pub async fn lookup_by_contact(context: &Context, contact_id: u32) -> Result<Option<Self>> {
+    pub async fn lookup_by_contact(
+        context: &Context,
+        contact_id: ContactId,
+    ) -> Result<Option<Self>> {
         ChatIdBlocked::lookup_by_contact(context, contact_id)
             .await
             .map(|lookup| lookup.map(|chat| chat.id))
@@ -166,7 +169,7 @@ impl ChatId {
     /// This is an internal API, if **a user action** needs to get a chat
     /// [`ChatId::create_for_contact`] should be used as this also scales up the
     /// [`Contact`]'s origin.
-    pub async fn get_for_contact(context: &Context, contact_id: u32) -> Result<Self> {
+    pub async fn get_for_contact(context: &Context, contact_id: ContactId) -> Result<Self> {
         ChatIdBlocked::get_for_contact(context, contact_id, Blocked::Not)
             .await
             .map(|chat| chat.id)
@@ -176,7 +179,7 @@ impl ChatId {
     ///
     /// This should be used when **a user action** creates a chat 1:1, it ensures the chat
     /// exists, is unblocked and scales the [`Contact`]'s origin.
-    pub async fn create_for_contact(context: &Context, contact_id: u32) -> Result<Self> {
+    pub async fn create_for_contact(context: &Context, contact_id: ContactId) -> Result<Self> {
         ChatId::create_for_contact_with_blocked(context, contact_id, Blocked::Not).await
     }
 
@@ -185,7 +188,7 @@ impl ChatId {
     /// `create_blocked` won't block already unblocked chats again.
     pub(crate) async fn create_for_contact_with_blocked(
         context: &Context,
-        contact_id: u32,
+        contact_id: ContactId,
         create_blocked: Blocked,
     ) -> Result<Self> {
         let chat_id = match ChatIdBlocked::lookup_by_contact(context, contact_id).await? {
@@ -420,7 +423,7 @@ impl ChatId {
         context: &Context,
         protect: ProtectionStatus,
         promote: bool,
-        from_id: u32,
+        from_id: ContactId,
     ) -> Result<()> {
         let msg_text = context.stock_protection_msg(protect, from_id).await;
         let cmd = match protect {
@@ -1628,7 +1631,11 @@ pub(crate) async fn get_broadcast_icon(context: &Context) -> Result<String> {
     Ok(icon)
 }
 
-async fn update_special_chat_name(context: &Context, contact_id: u32, name: String) -> Result<()> {
+async fn update_special_chat_name(
+    context: &Context,
+    contact_id: ContactId,
+    name: String,
+) -> Result<()> {
     if let Some(chat_id) = ChatId::lookup_by_contact(context, contact_id).await? {
         // the `!= name` condition avoids unneeded writes
         context
@@ -1675,9 +1682,15 @@ impl ChatIdBlocked {
     /// Searches the database for the 1:1 chat with this contact.
     ///
     /// If no chat is found `None` is returned.
-    pub async fn lookup_by_contact(context: &Context, contact_id: u32) -> Result<Option<Self>> {
+    pub async fn lookup_by_contact(
+        context: &Context,
+        contact_id: ContactId,
+    ) -> Result<Option<Self>> {
         ensure!(context.sql.is_open().await, "Database not available");
-        ensure!(contact_id > 0, "Invalid contact id requested");
+        ensure!(
+            contact_id > ContactId::new(0),
+            "Invalid contact id requested"
+        );
 
         context
             .sql
@@ -1706,11 +1719,14 @@ impl ChatIdBlocked {
     /// state.
     pub async fn get_for_contact(
         context: &Context,
-        contact_id: u32,
+        contact_id: ContactId,
         create_blocked: Blocked,
     ) -> Result<Self> {
         ensure!(context.sql.is_open().await, "Database not available");
-        ensure!(contact_id > 0, "Invalid contact id requested");
+        ensure!(
+            contact_id > ContactId::new(0),
+            "Invalid contact id requested"
+        );
 
         if let Some(res) = Self::lookup_by_contact(context, contact_id).await? {
             // Already exists, no need to create.
@@ -1914,7 +1930,7 @@ async fn prepare_msg_common(
 pub async fn is_contact_in_chat(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<bool> {
     // this function works for group and for normal chats, however, it is more useful
     // for group chats.
@@ -1925,7 +1941,7 @@ pub async fn is_contact_in_chat(
         .sql
         .exists(
             "SELECT COUNT(*) FROM chats_contacts WHERE chat_id=? AND contact_id=?;",
-            paramsv![chat_id, contact_id as i32],
+            paramsv![chat_id, contact_id],
         )
         .await?;
     Ok(exists)
@@ -2227,9 +2243,12 @@ pub async fn get_chat_msgs(
         |row: &rusqlite::Row| {
             // is_info logic taken from Message.is_info()
             let params = row.get::<_, String>("param")?;
-            let (from_id, to_id) = (row.get::<_, u32>("from_id")?, row.get::<_, u32>("to_id")?);
-            let is_info_msg: bool = from_id == DC_CONTACT_ID_INFO as u32
-                || to_id == DC_CONTACT_ID_INFO as u32
+            let (from_id, to_id) = (
+                row.get::<_, ContactId>("from_id")?,
+                row.get::<_, ContactId>("to_id")?,
+            );
+            let is_info_msg: bool = from_id == DC_CONTACT_ID_INFO
+                || to_id == DC_CONTACT_ID_INFO
                 || match Params::from_str(&params) {
                     Ok(p) => {
                         let cmd = p.get_cmd();
@@ -2530,7 +2549,7 @@ pub async fn get_next_media(
 }
 
 /// Returns a vector of contact IDs for given chat ID.
-pub async fn get_chat_contacts(context: &Context, chat_id: ChatId) -> Result<Vec<u32>> {
+pub async fn get_chat_contacts(context: &Context, chat_id: ChatId) -> Result<Vec<ContactId>> {
     // Normal chats do not include SELF.  Group chats do (as it may happen that one is deleted from a
     // groupchat but the chats stays visible, moreover, this makes displaying lists easier)
 
@@ -2544,7 +2563,7 @@ pub async fn get_chat_contacts(context: &Context, chat_id: ChatId) -> Result<Vec
               WHERE cc.chat_id=?
               ORDER BY c.id=1, LOWER(c.name||c.addr), c.id;",
             paramsv![chat_id],
-            |row| row.get::<_, u32>(0),
+            |row| row.get::<_, ContactId>(0),
             |ids| ids.collect::<Result<Vec<_>, _>>().map_err(Into::into),
         )
         .await?;
@@ -2651,13 +2670,13 @@ pub async fn create_broadcast_list(context: &Context) -> Result<ChatId> {
 pub(crate) async fn add_to_chat_contacts_table(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<()> {
     context
         .sql
         .execute(
             "INSERT INTO chats_contacts (chat_id, contact_id) VALUES(?, ?)",
-            paramsv![chat_id, contact_id as i32],
+            paramsv![chat_id, contact_id],
         )
         .await?;
     Ok(())
@@ -2667,13 +2686,13 @@ pub(crate) async fn add_to_chat_contacts_table(
 pub(crate) async fn remove_from_chat_contacts_table(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<()> {
     context
         .sql
         .execute(
             "DELETE FROM chats_contacts WHERE chat_id=? AND contact_id=?",
-            paramsv![chat_id, contact_id as i32],
+            paramsv![chat_id, contact_id],
         )
         .await?;
     Ok(())
@@ -2683,7 +2702,7 @@ pub(crate) async fn remove_from_chat_contacts_table(
 pub async fn add_contact_to_chat(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<()> {
     add_contact_to_chat_ex(context, chat_id, contact_id, false).await?;
     Ok(())
@@ -2692,7 +2711,7 @@ pub async fn add_contact_to_chat(
 pub(crate) async fn add_contact_to_chat_ex(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
     from_handshake: bool,
 ) -> Result<bool> {
     ensure!(!chat_id.is_special(), "can not add member to special chats");
@@ -2769,9 +2788,8 @@ pub(crate) async fn add_contact_to_chat_ex(
     if chat.typ == Chattype::Group && chat.is_promoted() {
         msg.viewtype = Viewtype::Text;
 
-        msg.text = Some(
-            stock_str::msg_add_member(context, contact.get_addr(), DC_CONTACT_ID_SELF as u32).await,
-        );
+        msg.text =
+            Some(stock_str::msg_add_member(context, contact.get_addr(), DC_CONTACT_ID_SELF).await);
         msg.param.set_cmd(SystemMessage::MemberAddedToGroup);
         msg.param.set(Param::Arg, contact.get_addr());
         msg.param.set_int(Param::Arg2, from_handshake.into());
@@ -2874,7 +2892,7 @@ pub async fn set_muted(context: &Context, chat_id: ChatId, duration: MuteDuratio
 pub async fn remove_contact_from_chat(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<()> {
     ensure!(
         !chat_id.is_special(),
@@ -2903,15 +2921,14 @@ pub async fn remove_contact_from_chat(
                         msg.viewtype = Viewtype::Text;
                         if contact.id == DC_CONTACT_ID_SELF {
                             set_group_explicitly_left(context, &chat.grpid).await?;
-                            msg.text = Some(
-                                stock_str::msg_group_left(context, DC_CONTACT_ID_SELF as u32).await,
-                            );
+                            msg.text =
+                                Some(stock_str::msg_group_left(context, DC_CONTACT_ID_SELF).await);
                         } else {
                             msg.text = Some(
                                 stock_str::msg_del_member(
                                     context,
                                     contact.get_addr(),
-                                    DC_CONTACT_ID_SELF as u32,
+                                    DC_CONTACT_ID_SELF,
                                 )
                                 .await,
                             );
@@ -3004,13 +3021,8 @@ pub async fn set_chat_name(context: &Context, chat_id: ChatId, new_name: &str) -
             if chat.is_promoted() && !chat.is_mailing_list() && chat.typ != Chattype::Broadcast {
                 msg.viewtype = Viewtype::Text;
                 msg.text = Some(
-                    stock_str::msg_grp_name(
-                        context,
-                        &chat.name,
-                        &new_name,
-                        DC_CONTACT_ID_SELF as u32,
-                    )
-                    .await,
+                    stock_str::msg_grp_name(context, &chat.name, &new_name, DC_CONTACT_ID_SELF)
+                        .await,
                 );
                 msg.param.set_cmd(SystemMessage::GroupNameChanged);
                 if !chat.name.is_empty() {
@@ -3063,7 +3075,7 @@ pub async fn set_chat_profile_image(
     if new_image.as_ref().is_empty() {
         chat.param.remove(Param::ProfileImage);
         msg.param.remove(Param::Arg);
-        msg.text = Some(stock_str::msg_grp_img_deleted(context, DC_CONTACT_ID_SELF as u32).await);
+        msg.text = Some(stock_str::msg_grp_img_deleted(context, DC_CONTACT_ID_SELF).await);
     } else {
         let mut image_blob = match BlobObject::from_path(context, Path::new(new_image.as_ref())) {
             Ok(blob) => Ok(blob),
@@ -3077,7 +3089,7 @@ pub async fn set_chat_profile_image(
         image_blob.recode_to_avatar_size(context).await?;
         chat.param.set(Param::ProfileImage, image_blob.as_name());
         msg.param.set(Param::Arg, image_blob.as_name());
-        msg.text = Some(stock_str::msg_grp_img_changed(context, DC_CONTACT_ID_SELF as u32).await);
+        msg.text = Some(stock_str::msg_grp_img_changed(context, DC_CONTACT_ID_SELF).await);
     }
     chat.update_param(context).await?;
     if chat.is_promoted() && !chat.is_mailing_list() {
@@ -3905,7 +3917,7 @@ mod tests {
     async fn test_self_talk() -> Result<()> {
         let t = TestContext::new_alice().await;
         let chat = &t.get_self_chat().await;
-        assert_eq!(DC_CONTACT_ID_SELF, 1);
+        assert_eq!(DC_CONTACT_ID_SELF, ContactId::new(1));
         assert!(!chat.id.is_special());
         assert!(chat.is_self_talk());
         assert!(chat.visibility == ChatVisibility::Normal);
@@ -4322,7 +4334,7 @@ mod tests {
         let contact1 = Contact::create(&context.ctx, "bob", "bob@mail.de")
             .await
             .unwrap();
-        assert_ne!(contact1, 0);
+        assert_ne!(contact1, ContactId::new(0));
 
         let chat_id = ChatId::create_for_contact(&context.ctx, contact1)
             .await
@@ -4527,7 +4539,7 @@ mod tests {
 
         // create contact, then unblocked chat
         let contact_id = Contact::create(&ctx, "", "bob@foo.de").await.unwrap();
-        assert_ne!(contact_id, 0);
+        assert_ne!(contact_id, ContactId::new(0));
         let found = ChatId::lookup_by_contact(&ctx, contact_id).await.unwrap();
         assert!(found.is_none());
 
@@ -4553,10 +4565,14 @@ mod tests {
         assert_eq!(chat2.blocked, Blocked::Yes);
 
         // test nonexistent contact
-        let found = ChatId::lookup_by_contact(&ctx, 1234).await.unwrap();
+        let found = ChatId::lookup_by_contact(&ctx, ContactId::new(1234))
+            .await
+            .unwrap();
         assert!(found.is_none());
 
-        let found = ChatIdBlocked::lookup_by_contact(&ctx, 1234).await.unwrap();
+        let found = ChatIdBlocked::lookup_by_contact(&ctx, ContactId::new(1234))
+            .await
+            .unwrap();
         assert!(found.is_none());
     }
 
diff --git a/src/chatlist.rs b/src/chatlist.rs
index 075c83227..bae795bbd 100644
--- a/src/chatlist.rs
+++ b/src/chatlist.rs
@@ -8,7 +8,7 @@ use crate::constants::{
     DC_CONTACT_ID_SELF, DC_CONTACT_ID_UNDEFINED, DC_GCL_ADD_ALLDONE_HINT, DC_GCL_ARCHIVED_ONLY,
     DC_GCL_FOR_FORWARDING, DC_GCL_NO_SPECIALS,
 };
-use crate::contact::Contact;
+use crate::contact::{Contact, ContactId};
 use crate::context::Context;
 use crate::ephemeral::delete_expired_messages;
 use crate::message::{Message, MessageState, MsgId};
@@ -85,7 +85,7 @@ impl Chatlist {
         context: &Context,
         listflags: usize,
         query: Option<&str>,
-        query_contact_id: Option<u32>,
+        query_contact_id: Option<ContactId>,
     ) -> Result<Self> {
         let flag_archived_only = 0 != listflags & DC_GCL_ARCHIVED_ONLY;
         let flag_for_forwarding = 0 != listflags & DC_GCL_FOR_FORWARDING;
@@ -147,7 +147,7 @@ impl Chatlist {
                    AND c.id IN(SELECT chat_id FROM chats_contacts WHERE contact_id=?2)
                  GROUP BY c.id
                  ORDER BY c.archived=?3 DESC, IFNULL(m.timestamp,c.created_timestamp) DESC, m.id DESC;",
-                paramsv![MessageState::OutDraft, query_contact_id as i32, ChatVisibility::Pinned],
+                paramsv![MessageState::OutDraft, query_contact_id, ChatVisibility::Pinned],
                 process_row,
                 process_rows,
             ).await?
diff --git a/src/constants.rs b/src/constants.rs
index 7fa3f347b..294718e1a 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -4,6 +4,7 @@ use once_cell::sync::Lazy;
 use serde::{Deserialize, Serialize};
 
 use crate::chat::ChatId;
+use crate::contact::ContactId;
 
 pub static DC_VERSION_STR: Lazy<String> = Lazy::new(|| env!("CARGO_PKG_VERSION").to_string());
 
@@ -179,11 +180,11 @@ pub const DC_ELLIPSIS: &str = "[...]";
 /// `char`s), not Unicode Grapheme Clusters.
 pub const DC_DESIRED_TEXT_LEN: usize = 5000;
 
-pub const DC_CONTACT_ID_UNDEFINED: u32 = 0;
-pub const DC_CONTACT_ID_SELF: u32 = 1;
-pub const DC_CONTACT_ID_INFO: u32 = 2;
-pub const DC_CONTACT_ID_DEVICE: u32 = 5;
-pub const DC_CONTACT_ID_LAST_SPECIAL: u32 = 9;
+pub const DC_CONTACT_ID_UNDEFINED: ContactId = ContactId::new(0);
+pub const DC_CONTACT_ID_SELF: ContactId = ContactId::new(1);
+pub const DC_CONTACT_ID_INFO: ContactId = ContactId::new(2);
+pub const DC_CONTACT_ID_DEVICE: ContactId = ContactId::new(5);
+pub const DC_CONTACT_ID_LAST_SPECIAL: ContactId = ContactId::new(9);
 
 // decorative address that is used for DC_CONTACT_ID_DEVICE
 // when an api that returns an email is called.
diff --git a/src/contact.rs b/src/contact.rs
index 651283cca..a08e7b0e3 100644
--- a/src/contact.rs
+++ b/src/contact.rs
@@ -1,12 +1,14 @@
 //! Contacts module
 
 use std::convert::{TryFrom, TryInto};
+use std::fmt;
 
 use anyhow::{bail, ensure, Context as _, Result};
 use async_std::path::PathBuf;
 use deltachat_derive::{FromSql, ToSql};
 use once_cell::sync::Lazy;
 use regex::Regex;
+use serde::{Deserialize, Serialize};
 
 use crate::aheader::EncryptPreference;
 use crate::chat::ChatId;
@@ -27,6 +29,67 @@ use crate::param::{Param, Params};
 use crate::peerstate::{Peerstate, PeerstateVerifiedStatus};
 use crate::{chat, stock_str};
 
+/// Contact ID, including reserved IDs.
+///
+/// Some contact IDs are reserved to identify special contacts.  This
+/// type can represent both the special as well as normal contacts.
+#[derive(
+    Debug, Copy, Clone, Default, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize,
+)]
+pub struct ContactId(u32);
+
+impl ContactId {
+    /// Creates a new [`ContactId`].
+    pub const fn new(id: u32) -> ContactId {
+        ContactId(id)
+    }
+
+    /// Bad evil escape hatch, do not use.
+    pub const fn to_u32(&self) -> u32 {
+        self.0
+    }
+}
+
+impl fmt::Display for ContactId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+        // TODO: Something like this
+        // if self == DC_CONTACT_ID_UNDEFINED {
+        //     write!(f, "Contact#Undefined")
+        // } else if self == DC_CONTACT_ID_SELF {
+        //     write!(f, "Contact#Self")
+        // } else if self == DC_CONTACT_ID_INFO {
+        //     write!(f, "Contact#Info")
+        // } else if self == DC_CONTACT_ID_DEVICE {
+        //     write!(f, "Contact#Device")
+        // } else if self <= DC_CONTACT_ID_LAST_SPECIAL {
+        //     write!(f, "Contact#Special{}", self.0)
+        // } else {
+        //     write!(f, "Contact#{}", self.0)
+        // }
+    }
+}
+
+/// Allow converting [`ContactId`] to an SQLite type.
+impl rusqlite::types::ToSql for ContactId {
+    fn to_sql(&self) -> rusqlite::Result<rusqlite::types::ToSqlOutput> {
+        let val = rusqlite::types::Value::Integer(i64::from(self.0));
+        let out = rusqlite::types::ToSqlOutput::Owned(val);
+        Ok(out)
+    }
+}
+
+/// Allow converting an SQLite integer directly into [`ContactId`].
+impl rusqlite::types::FromSql for ContactId {
+    fn column_result(value: rusqlite::types::ValueRef) -> rusqlite::types::FromSqlResult<Self> {
+        i64::column_result(value).and_then(|val| {
+            val.try_into()
+                .map(ContactId::new)
+                .map_err(|_| rusqlite::types::FromSqlError::OutOfRange(val))
+        })
+    }
+}
+
 /// An object representing a single contact in memory.
 ///
 /// The contact object is not updated.
@@ -48,7 +111,7 @@ pub struct Contact {
     ///   `dc_set_config` using "addr".
     ///
     /// Normal contact IDs are larger than these special ones (larger than DC_CONTACT_ID_LAST_SPECIAL).
-    pub id: u32,
+    pub id: ContactId,
 
     /// Contact name. It is recommended to use `Contact::get_name`,
     /// `Contact::get_display_name` or `Contact::get_name_n_addr` to access this field.
@@ -183,7 +246,7 @@ impl Default for VerifiedStatus {
 }
 
 impl Contact {
-    pub async fn load_from_db(context: &Context, contact_id: u32) -> Result<Self> {
+    pub async fn load_from_db(context: &Context, contact_id: ContactId) -> Result<Self> {
         let mut contact = context
             .sql
             .query_row(
@@ -191,7 +254,7 @@ impl Contact {
                 c.authname, c.param, c.status
                FROM contacts c
               WHERE c.id=?;",
-                paramsv![contact_id as i32],
+                paramsv![contact_id],
                 |row| {
                     let name: String = row.get(0)?;
                     let addr: String = row.get(1)?;
@@ -245,18 +308,18 @@ impl Contact {
     }
 
     /// Check if a contact is blocked.
-    pub async fn is_blocked_load(context: &Context, id: u32) -> Result<bool> {
+    pub async fn is_blocked_load(context: &Context, id: ContactId) -> Result<bool> {
         let blocked = Self::load_from_db(context, id).await?.blocked;
         Ok(blocked)
     }
 
     /// Block the given contact.
-    pub async fn block(context: &Context, id: u32) -> Result<()> {
+    pub async fn block(context: &Context, id: ContactId) -> Result<()> {
         set_block_contact(context, id, true).await
     }
 
     /// Unblock the given contact.
-    pub async fn unblock(context: &Context, id: u32) -> Result<()> {
+    pub async fn unblock(context: &Context, id: ContactId) -> Result<()> {
         set_block_contact(context, id, false).await
     }
 
@@ -269,7 +332,7 @@ impl Contact {
     /// a bunch of addresses.
     ///
     /// May result in a `#DC_EVENT_CONTACTS_CHANGED` event.
-    pub async fn create(context: &Context, name: &str, addr: &str) -> Result<u32> {
+    pub async fn create(context: &Context, name: &str, addr: &str) -> Result<ContactId> {
         let name = improve_single_line_input(name);
         ensure!(!addr.is_empty(), "Cannot create contact with empty address");
 
@@ -292,12 +355,12 @@ impl Contact {
     }
 
     /// Mark messages from a contact as noticed.
-    pub async fn mark_noticed(context: &Context, id: u32) -> Result<()> {
+    pub async fn mark_noticed(context: &Context, id: ContactId) -> Result<()> {
         context
             .sql
             .execute(
                 "UPDATE msgs SET state=? WHERE from_id=? AND state=?;",
-                paramsv![MessageState::InNoticed, id as i32, MessageState::InFresh],
+                paramsv![MessageState::InNoticed, id, MessageState::InFresh],
             )
             .await?;
         Ok(())
@@ -313,7 +376,7 @@ impl Contact {
         context: &Context,
         addr: &str,
         min_origin: Origin,
-    ) -> Result<Option<u32>> {
+    ) -> Result<Option<ContactId>> {
         if addr.is_empty() {
             bail!("lookup_id_by_addr: empty address");
         }
@@ -333,7 +396,7 @@ impl Contact {
             AND id>?2 AND origin>=?3 AND blocked=0;",
                 paramsv![
                     addr_normalized,
-                    DC_CONTACT_ID_LAST_SPECIAL as i32,
+                    DC_CONTACT_ID_LAST_SPECIAL,
                     min_origin as u32,
                 ],
             )
@@ -371,7 +434,7 @@ impl Contact {
         name: &str,
         addr: &str,
         mut origin: Origin,
-    ) -> Result<(u32, Modifier)> {
+    ) -> Result<(ContactId, Modifier)> {
         let mut sth_modified = Modifier::None;
 
         ensure!(!addr.is_empty(), "Can not add_or_lookup empty address");
@@ -500,7 +563,7 @@ impl Contact {
                         paramsv![Chattype::Single, isize::try_from(row_id)?]
                     ).await?;
                     if let Some(chat_id) = chat_id {
-                        let contact = Contact::get_by_id(context, row_id as u32).await?;
+                        let contact = Contact::get_by_id(context, ContactId::new(row_id)).await?;
                         let chat_name = contact.get_display_name();
                         match context
                             .sql
@@ -557,7 +620,7 @@ impl Contact {
             }
         }
 
-        Ok((row_id, sth_modified))
+        Ok((ContactId::new(row_id), sth_modified))
     }
 
     /// Add a number of contacts.
@@ -617,7 +680,7 @@ impl Contact {
         context: &Context,
         listflags: u32,
         query: Option<impl AsRef<str>>,
-    ) -> Result<Vec<u32>> {
+    ) -> Result<Vec<ContactId>> {
         let self_addr = context
             .get_config(Config::ConfiguredAddr)
             .await?
@@ -644,16 +707,16 @@ impl Contact {
                  ORDER BY LOWER(iif(c.name='',c.authname,c.name)||c.addr),c.id;",
                     paramsv![
                         self_addr,
-                        DC_CONTACT_ID_LAST_SPECIAL as i32,
+                        DC_CONTACT_ID_LAST_SPECIAL,
                         Origin::IncomingReplyTo,
                         s3str_like_cmd,
                         s3str_like_cmd,
                         if flag_verified_only { 0i32 } else { 1i32 },
                     ],
-                    |row| row.get::<_, i32>(0),
+                    |row| row.get::<_, ContactId>(0),
                     |ids| {
                         for id in ids {
-                            ret.push(id? as u32);
+                            ret.push(id?);
                         }
                         Ok(())
                     },
@@ -690,13 +753,13 @@ impl Contact {
                  ORDER BY LOWER(iif(name='',authname,name)||addr),id;",
                     paramsv![
                         self_addr,
-                        DC_CONTACT_ID_LAST_SPECIAL as i32,
+                        DC_CONTACT_ID_LAST_SPECIAL,
                         Origin::IncomingReplyTo
                     ],
-                    |row| row.get::<_, i32>(0),
+                    |row| row.get::<_, ContactId>(0),
                     |ids| {
                         for id in ids {
-                            ret.push(id? as u32);
+                            ret.push(id?);
                         }
                         Ok(())
                     },
@@ -767,7 +830,7 @@ impl Contact {
     }
 
     /// Get blocked contacts.
-    pub async fn get_all_blocked(context: &Context) -> Result<Vec<u32>> {
+    pub async fn get_all_blocked(context: &Context) -> Result<Vec<ContactId>> {
         Contact::update_blocked_mailinglist_contacts(context)
             .await
             .context("cannot update blocked mailinglist contacts")?;
@@ -776,8 +839,8 @@ impl Contact {
             .sql
             .query_map(
                 "SELECT id FROM contacts WHERE id>? AND blocked!=0 ORDER BY LOWER(iif(name='',authname,name)||addr),id;",
-                paramsv![DC_CONTACT_ID_LAST_SPECIAL as i32],
-                |row| row.get::<_, u32>(0),
+                paramsv![DC_CONTACT_ID_LAST_SPECIAL],
+                |row| row.get::<_, ContactId>(0),
                 |ids| {
                     ids.collect::<std::result::Result<Vec<_>, _>>()
                         .map_err(Into::into)
@@ -792,7 +855,7 @@ impl Contact {
     /// This function returns a string explaining the encryption state
     /// of the contact and if the connection is encrypted the
     /// fingerprints of the keys involved.
-    pub async fn get_encrinfo(context: &Context, contact_id: u32) -> Result<String> {
+    pub async fn get_encrinfo(context: &Context, contact_id: ContactId) -> Result<String> {
         ensure!(
             contact_id > DC_CONTACT_ID_LAST_SPECIAL,
             "Can not provide encryption info for special contact"
@@ -861,7 +924,7 @@ impl Contact {
     /// possible as the contact is in use. In this case, the contact can be blocked.
     ///
     /// May result in a `#DC_EVENT_CONTACTS_CHANGED` event.
-    pub async fn delete(context: &Context, contact_id: u32) -> Result<()> {
+    pub async fn delete(context: &Context, contact_id: ContactId) -> Result<()> {
         ensure!(
             contact_id > DC_CONTACT_ID_LAST_SPECIAL,
             "Can not delete special contact"
@@ -871,17 +934,14 @@ impl Contact {
             .sql
             .count(
                 "SELECT COUNT(*) FROM chats_contacts WHERE contact_id=?;",
-                paramsv![contact_id as i32],
+                paramsv![contact_id],
             )
             .await?;
 
         if count_chats == 0 {
             match context
                 .sql
-                .execute(
-                    "DELETE FROM contacts WHERE id=?;",
-                    paramsv![contact_id as i32],
-                )
+                .execute("DELETE FROM contacts WHERE id=?;", paramsv![contact_id])
                 .await
             {
                 Ok(_) => {
@@ -907,7 +967,7 @@ impl Contact {
     /// For contact DC_CONTACT_ID_SELF (1), the function returns sth.
     /// like "Me" in the selected language and the email address
     /// defined by dc_set_config().
-    pub async fn get_by_id(context: &Context, contact_id: u32) -> Result<Contact> {
+    pub async fn get_by_id(context: &Context, contact_id: ContactId) -> Result<Contact> {
         let contact = Contact::load_from_db(context, contact_id).await?;
 
         Ok(contact)
@@ -919,7 +979,7 @@ impl Contact {
             .sql
             .execute(
                 "UPDATE contacts SET param=? WHERE id=?",
-                paramsv![self.param.to_string(), self.id as i32],
+                paramsv![self.param.to_string(), self.id],
             )
             .await?;
         Ok(())
@@ -931,14 +991,14 @@ impl Contact {
             .sql
             .execute(
                 "UPDATE contacts SET status=? WHERE id=?",
-                paramsv![self.status, self.id as i32],
+                paramsv![self.status, self.id],
             )
             .await?;
         Ok(())
     }
 
     /// Get the ID of the contact.
-    pub fn get_id(&self) -> u32 {
+    pub fn get_id(&self) -> ContactId {
         self.id
     }
 
@@ -1065,7 +1125,7 @@ impl Contact {
     pub async fn addr_equals_contact(
         context: &Context,
         addr: &str,
-        contact_id: u32,
+        contact_id: ContactId,
     ) -> Result<bool> {
         if addr.is_empty() {
             return Ok(false);
@@ -1091,13 +1151,13 @@ impl Contact {
             .sql
             .count(
                 "SELECT COUNT(*) FROM contacts WHERE id>?;",
-                paramsv![DC_CONTACT_ID_LAST_SPECIAL as i32],
+                paramsv![DC_CONTACT_ID_LAST_SPECIAL],
             )
             .await?;
         Ok(count)
     }
 
-    pub async fn real_exists_by_id(context: &Context, contact_id: u32) -> Result<bool> {
+    pub async fn real_exists_by_id(context: &Context, contact_id: ContactId) -> Result<bool> {
         if contact_id <= DC_CONTACT_ID_LAST_SPECIAL {
             return Ok(false);
         }
@@ -1106,7 +1166,7 @@ impl Contact {
             .sql
             .exists(
                 "SELECT COUNT(*) FROM contacts WHERE id=?;",
-                paramsv![contact_id as i32],
+                paramsv![contact_id],
             )
             .await?;
         Ok(exists)
@@ -1114,14 +1174,14 @@ impl Contact {
 
     pub async fn scaleup_origin_by_id(
         context: &Context,
-        contact_id: u32,
+        contact_id: ContactId,
         origin: Origin,
     ) -> Result<()> {
         context
             .sql
             .execute(
                 "UPDATE contacts SET origin=? WHERE id=? AND origin<?;",
-                paramsv![origin, contact_id as i32, origin],
+                paramsv![origin, contact_id, origin],
             )
             .await?;
         Ok(())
@@ -1165,7 +1225,11 @@ fn sanitize_name_and_addr(name: &str, addr: &str) -> (String, String) {
     }
 }
 
-async fn set_block_contact(context: &Context, contact_id: u32, new_blocking: bool) -> Result<()> {
+async fn set_block_contact(
+    context: &Context,
+    contact_id: ContactId,
+    new_blocking: bool,
+) -> Result<()> {
     ensure!(
         contact_id > DC_CONTACT_ID_LAST_SPECIAL,
         "Can't block special contact {}",
@@ -1179,7 +1243,7 @@ async fn set_block_contact(context: &Context, contact_id: u32, new_blocking: boo
             .sql
             .execute(
                 "UPDATE contacts SET blocked=? WHERE id=?;",
-                paramsv![i32::from(new_blocking), contact_id as i32],
+                paramsv![i32::from(new_blocking), contact_id],
             )
             .await?;
 
@@ -1230,7 +1294,7 @@ WHERE type=? AND id IN (
 /// this typically happens if we see message with our own profile image, sent from another device.
 pub(crate) async fn set_profile_image(
     context: &Context,
-    contact_id: u32,
+    contact_id: ContactId,
     profile_image: &AvatarAction,
     was_encrypted: bool,
 ) -> Result<()> {
@@ -1277,7 +1341,7 @@ pub(crate) async fn set_profile_image(
 /// between Delta Chat devices.
 pub(crate) async fn set_status(
     context: &Context,
-    contact_id: u32,
+    contact_id: ContactId,
     status: String,
     encrypted: bool,
     has_chat_version: bool,
@@ -1303,7 +1367,7 @@ pub(crate) async fn set_status(
 /// Updates last seen timestamp of the contact if it is earlier than the given `timestamp`.
 pub(crate) async fn update_last_seen(
     context: &Context,
-    contact_id: u32,
+    contact_id: ContactId,
     timestamp: i64,
 ) -> Result<()> {
     ensure!(
@@ -1474,7 +1538,7 @@ mod tests {
             Origin::IncomingReplyTo,
         )
         .await?;
-        assert_ne!(id, 0);
+        assert_ne!(id, ContactId::new(0));
 
         let contact = Contact::load_from_db(&context.ctx, id).await.unwrap();
         assert_eq!(contact.get_name(), "");
@@ -1629,7 +1693,7 @@ mod tests {
 
         // check SELF
         let contact = Contact::load_from_db(&t, DC_CONTACT_ID_SELF).await.unwrap();
-        assert_eq!(DC_CONTACT_ID_SELF, 1);
+        assert_eq!(DC_CONTACT_ID_SELF, ContactId::new(1));
         assert_eq!(contact.get_name(), stock_str::self_msg(&t).await);
         assert_eq!(contact.get_addr(), ""); // we're not configured
         assert!(!contact.is_blocked());
diff --git a/src/dc_receive_imf.rs b/src/dc_receive_imf.rs
index 44ad9ec54..de1a8c537 100644
--- a/src/dc_receive_imf.rs
+++ b/src/dc_receive_imf.rs
@@ -18,7 +18,7 @@ use crate::constants::{
     DC_CONTACT_ID_SELF,
 };
 use crate::contact::{
-    addr_cmp, may_be_valid_addr, normalize_name, Contact, Origin, VerifiedStatus,
+    addr_cmp, may_be_valid_addr, normalize_name, Contact, ContactId, Origin, VerifiedStatus,
 };
 use crate::context::Context;
 use crate::dc_tools::{dc_create_id, dc_extract_grpid_from_rfc724_mid, dc_smeared_time};
@@ -199,7 +199,7 @@ pub(crate) async fn dc_receive_imf_inner(
         .map_or(rcvd_timestamp, |value| min(value, rcvd_timestamp));
 
     if mime_parser.is_system_message == SystemMessage::LocationStreamingEnabled {
-        let better_msg = stock_str::msg_location_enabled_by(context, from_id as u32).await;
+        let better_msg = stock_str::msg_location_enabled_by(context, from_id).await;
         set_better_msg(&mut mime_parser, &better_msg);
     }
 
@@ -283,7 +283,7 @@ pub(crate) async fn dc_receive_imf_inner(
     }
 
     if let Some(avatar_action) = &mime_parser.user_avatar {
-        if from_id != 0
+        if from_id != ContactId::new(0)
             && context
                 .update_contacts_timestamp(from_id, Param::AvatarTimestamp, sent_timestamp)
                 .await?
@@ -311,7 +311,7 @@ pub(crate) async fn dc_receive_imf_inner(
     // Ignore MDNs though, as they never contain the signature even if user has set it.
     if mime_parser.mdn_reports.is_empty()
         && is_partial_download.is_none()
-        && from_id != 0
+        && from_id != ContactId::new(0)
         && context
             .update_contacts_timestamp(from_id, Param::StatusTimestamp, sent_timestamp)
             .await?
@@ -387,7 +387,7 @@ pub async fn from_field_to_contact_id(
     context: &Context,
     from_address_list: &[SingleInfo],
     prevent_rename: bool,
-) -> Result<(u32, bool, Origin)> {
+) -> Result<(ContactId, bool, Origin)> {
     let from_ids = dc_add_or_lookup_contacts_by_address_list(
         context,
         from_address_list,
@@ -420,7 +420,7 @@ pub async fn from_field_to_contact_id(
             "mail has an empty From header: {:?}", from_address_list
         );
 
-        Ok((0, false, Origin::Unknown))
+        Ok((ContactId::new(0), false, Origin::Unknown))
     }
 }
 
@@ -431,11 +431,11 @@ async fn add_parts(
     imf_raw: &[u8],
     incoming: bool,
     server_folder: &str,
-    to_ids: &[u32],
+    to_ids: &[ContactId],
     rfc724_mid: &str,
     sent_timestamp: i64,
     rcvd_timestamp: i64,
-    from_id: u32,
+    from_id: ContactId,
     seen: bool,
     is_partial_download: Option<u32>,
     needs_delete_job: &mut bool,
@@ -488,7 +488,7 @@ async fn add_parts(
     // - outgoing messages introduce a chat with the first to: address if they are sent by a messenger
     // - incoming messages introduce a chat only for known contacts if they are sent by a messenger
     // (of course, the user can add other chats manually later)
-    let to_id: u32;
+    let to_id: ContactId;
 
     let state: MessageState;
     if incoming {
@@ -524,7 +524,7 @@ async fn add_parts(
             securejoin_seen = false;
         }
 
-        let test_normal_chat = if from_id == 0 {
+        let test_normal_chat = if from_id == ContactId::new(0) {
             Default::default()
         } else {
             ChatIdBlocked::lookup_by_contact(context, from_id).await?
@@ -583,7 +583,7 @@ async fn add_parts(
         // In lookup_chat_by_reply() and create_or_lookup_group(), it can happen that the message is put into a chat
         // but the From-address is not a member of this chat.
         if let Some(chat_id) = chat_id {
-            if !chat::is_contact_in_chat(context, chat_id, from_id as u32).await? {
+            if !chat::is_contact_in_chat(context, chat_id, from_id).await? {
                 let chat = Chat::load_from_db(context, chat_id).await?;
                 if chat.is_protected() {
                     let s = stock_str::unknown_sender_for_chat(context).await;
@@ -1031,9 +1031,7 @@ async fn add_parts(
                     }
                     set_better_msg(
                         mime_parser,
-                        context
-                            .stock_protection_msg(new_status, from_id as u32)
-                            .await,
+                        context.stock_protection_msg(new_status, from_id).await,
                     );
                 }
             }
@@ -1156,8 +1154,8 @@ INSERT INTO msgs
         stmt.execute(paramsv![
             rfc724_mid,
             chat_id,
-            if trash { 0 } else { i64::from(from_id) },
-            if trash { 0 } else { i64::from(to_id) },
+            if trash { ContactId::new(0) } else { from_id },
+            if trash { ContactId::new(0) } else { to_id },
             sort_timestamp,
             sent_timestamp,
             rcvd_timestamp,
@@ -1256,7 +1254,7 @@ async fn save_locations(
     context: &Context,
     mime_parser: &MimeMessage,
     chat_id: ChatId,
-    from_id: u32,
+    from_id: ContactId,
     msg_id: MsgId,
 ) -> Result<()> {
     if chat_id.is_special() {
@@ -1335,8 +1333,8 @@ async fn lookup_chat_by_reply(
     context: &Context,
     mime_parser: &mut MimeMessage,
     parent: &Option<Message>,
-    from_id: u32,
-    to_ids: &[u32],
+    from_id: ContactId,
+    to_ids: &[ContactId],
 ) -> Result<Option<(ChatId, Blocked)>> {
     // Try to assign message to the same chat as the parent message.
 
@@ -1376,10 +1374,10 @@ async fn lookup_chat_by_reply(
 /// If it returns false, it shall be assigned to the parent chat.
 async fn is_probably_private_reply(
     context: &Context,
-    to_ids: &[u32],
+    to_ids: &[ContactId],
     mime_parser: &MimeMessage,
     parent_chat_id: ChatId,
-    from_id: u32,
+    from_id: ContactId,
 ) -> Result<bool> {
     // Usually we don't want to show private replies in the parent chat, but in the
     // 1:1 chat with the sender.
@@ -1416,18 +1414,18 @@ async fn create_or_lookup_group(
     mime_parser: &mut MimeMessage,
     allow_creation: bool,
     create_blocked: Blocked,
-    from_id: u32,
-    to_ids: &[u32],
+    from_id: ContactId,
+    to_ids: &[ContactId],
 ) -> Result<Option<(ChatId, Blocked)>> {
     let grpid = if let Some(grpid) = try_getting_grpid(mime_parser) {
         grpid
     } else if allow_creation {
-        let mut member_ids: Vec<u32> = to_ids.to_vec();
-        if !member_ids.contains(&(from_id as u32)) {
-            member_ids.push(from_id as u32);
+        let mut member_ids: Vec<ContactId> = to_ids.to_vec();
+        if !member_ids.contains(&(from_id)) {
+            member_ids.push(from_id);
         }
-        if !member_ids.contains(&(DC_CONTACT_ID_SELF as u32)) {
-            member_ids.push(DC_CONTACT_ID_SELF as u32);
+        if !member_ids.contains(&(DC_CONTACT_ID_SELF)) {
+            member_ids.push(DC_CONTACT_ID_SELF);
         }
 
         let res = create_adhoc_group(context, mime_parser, create_blocked, &member_ids)
@@ -1561,8 +1559,8 @@ async fn apply_group_changes(
     mime_parser: &mut MimeMessage,
     sent_timestamp: i64,
     chat_id: ChatId,
-    from_id: u32,
-    to_ids: &[u32],
+    from_id: ContactId,
+    to_ids: &[ContactId],
 ) -> Result<()> {
     let mut chat = Chat::load_from_db(context, chat_id).await?;
     if chat.typ != Chattype::Group {
@@ -1626,8 +1624,7 @@ async fn apply_group_changes(
                     send_event_chat_modified = true;
                 }
 
-                let better_msg =
-                    stock_str::msg_grp_name(context, old_name, grpname, from_id as u32).await;
+                let better_msg = stock_str::msg_grp_name(context, old_name, grpname, from_id).await;
                 set_better_msg(mime_parser, &better_msg);
                 mime_parser.is_system_message = SystemMessage::GroupNameChanged;
             }
@@ -1953,7 +1950,7 @@ async fn create_adhoc_group(
     context: &Context,
     mime_parser: &MimeMessage,
     create_blocked: Blocked,
-    member_ids: &[u32],
+    member_ids: &[ContactId],
 ) -> Result<Option<ChatId>> {
     if mime_parser.is_mailinglist_message() {
         info!(
@@ -2023,7 +2020,7 @@ async fn create_adhoc_group(
 /// This ensures that different Delta Chat clients generate the same group ID unless some of them
 /// are hidden in BCC. This group ID is sent by DC in the messages sent to this chat,
 /// so having the same ID prevents group split.
-async fn create_adhoc_grp_id(context: &Context, member_ids: &[u32]) -> Result<String> {
+async fn create_adhoc_grp_id(context: &Context, member_ids: &[ContactId]) -> Result<String> {
     let member_ids_str = member_ids
         .iter()
         .map(|x| x.to_string())
@@ -2070,8 +2067,8 @@ fn hex_hash(s: &str) -> String {
 async fn check_verified_properties(
     context: &Context,
     mimeparser: &MimeMessage,
-    from_id: u32,
-    to_ids: &[u32],
+    from_id: ContactId,
+    to_ids: &[ContactId],
 ) -> Result<()> {
     let contact = Contact::load_from_db(context, from_id).await?;
 
@@ -2118,7 +2115,7 @@ async fn check_verified_properties(
         .iter()
         .copied()
         .filter(|id| *id != DC_CONTACT_ID_SELF)
-        .collect::<Vec<u32>>();
+        .collect::<Vec<ContactId>>();
 
     if to_ids.is_empty() {
         return Ok(());
@@ -2301,7 +2298,7 @@ async fn dc_add_or_lookup_contacts_by_address_list(
     address_list: &[SingleInfo],
     origin: Origin,
     prevent_rename: bool,
-) -> Result<Vec<u32>> {
+) -> Result<Vec<ContactId>> {
     let mut contact_ids = BTreeSet::new();
     for info in address_list.iter() {
         let addr = &info.addr;
@@ -2317,7 +2314,7 @@ async fn dc_add_or_lookup_contacts_by_address_list(
             .insert(add_or_lookup_contact_by_addr(context, display_name, addr, origin).await?);
     }
 
-    Ok(contact_ids.into_iter().collect::<Vec<u32>>())
+    Ok(contact_ids.into_iter().collect::<Vec<ContactId>>())
 }
 
 /// Add contacts to database on receiving messages.
@@ -2326,7 +2323,7 @@ async fn add_or_lookup_contact_by_addr(
     display_name: Option<&str>,
     addr: &str,
     origin: Origin,
-) -> Result<u32> {
+) -> Result<ContactId> {
     if context.is_self_addr(addr).await? {
         return Ok(DC_CONTACT_ID_SELF);
     }
@@ -2334,8 +2331,6 @@ async fn add_or_lookup_contact_by_addr(
 
     let (row_id, _modified) =
         Contact::add_or_lookup(context, &display_name_normalized, addr, origin).await?;
-    ensure!(row_id > 0, "could not add contact: {:?}", addr);
-
     Ok(row_id)
 }
 
diff --git a/src/ephemeral.rs b/src/ephemeral.rs
index 38f59f241..d42e6cc43 100644
--- a/src/ephemeral.rs
+++ b/src/ephemeral.rs
@@ -69,6 +69,7 @@ use crate::chat::{send_msg, ChatId};
 use crate::constants::{
     Viewtype, DC_CHAT_ID_LAST_SPECIAL, DC_CHAT_ID_TRASH, DC_CONTACT_ID_DEVICE, DC_CONTACT_ID_SELF,
 };
+use crate::contact::ContactId;
 use crate::context::Context;
 use crate::dc_tools::time;
 use crate::download::MIN_DELETE_SERVER_AFTER;
@@ -212,7 +213,7 @@ impl ChatId {
 pub(crate) async fn stock_ephemeral_timer_changed(
     context: &Context,
     timer: Timer,
-    from_id: u32,
+    from_id: ContactId,
 ) -> String {
     match timer {
         Timer::Disabled => stock_str::msg_ephemeral_timer_disabled(context, from_id).await,
@@ -823,8 +824,8 @@ mod tests {
 
         // Check that if there is a message left, the text and metadata are gone
         if let Ok(msg) = Message::load_from_db(t, msg_id).await {
-            assert_eq!(msg.from_id, 0);
-            assert_eq!(msg.to_id, 0);
+            assert_eq!(msg.from_id, ContactId::new(0));
+            assert_eq!(msg.to_id, ContactId::new(0));
             assert!(msg.text.is_none_or_empty(), "{:?}", msg.text);
             let rawtxt: Option<String> = t
                 .sql
diff --git a/src/events.rs b/src/events.rs
index 4fea31a99..8ecbf23aa 100644
--- a/src/events.rs
+++ b/src/events.rs
@@ -7,6 +7,7 @@ use async_std::path::PathBuf;
 use strum::EnumProperty;
 
 use crate::chat::ChatId;
+use crate::contact::ContactId;
 use crate::ephemeral::Timer as EphemeralTimer;
 use crate::message::MsgId;
 
@@ -252,7 +253,7 @@ pub enum EventType {
     ///
     /// @param data1 (int) If set, this is the contact_id of an added contact that should be selected.
     #[strum(props(id = "2030"))]
-    ContactsChanged(Option<u32>),
+    ContactsChanged(Option<ContactId>),
 
     /// Location of one or more contact has changed.
     ///
@@ -260,7 +261,7 @@ pub enum EventType {
     ///     If the locations of several contacts have been changed,
     ///     eg. after calling dc_delete_all_locations(), this parameter is set to `None`.
     #[strum(props(id = "2035"))]
-    LocationChanged(Option<u32>),
+    LocationChanged(Option<ContactId>),
 
     /// Inform about the configuration progress started by configure().
     #[strum(props(id = "2041"))]
@@ -304,7 +305,10 @@ pub enum EventType {
     ///     800=vg-member-added-received received, shown as "bob@addr securely joined GROUP", only sent for the verified-group-protocol.
     ///     1000=Protocol finished for this contact.
     #[strum(props(id = "2060"))]
-    SecurejoinInviterProgress { contact_id: u32, progress: usize },
+    SecurejoinInviterProgress {
+        contact_id: ContactId,
+        progress: usize,
+    },
 
     /// Progress information of a secure-join handshake from the view of the joiner
     /// (Bob, the person who scans the QR code).
@@ -315,7 +319,10 @@ pub enum EventType {
     ///     400=vg-/vc-request-with-auth sent, typically shown as "alice@addr verified, introducing myself."
     ///     (Bob has verified alice and waits until Alice does the same for him)
     #[strum(props(id = "2061"))]
-    SecurejoinJoinerProgress { contact_id: u32, progress: usize },
+    SecurejoinJoinerProgress {
+        contact_id: ContactId,
+        progress: usize,
+    },
 
     /// The connectivity to the server changed.
     /// This means that you should refresh the connectivity view
diff --git a/src/job.rs b/src/job.rs
index 174dd33b0..c06258c50 100644
--- a/src/job.rs
+++ b/src/job.rs
@@ -9,7 +9,7 @@ use deltachat_derive::{FromSql, ToSql};
 use rand::{thread_rng, Rng};
 
 use crate::config::Config;
-use crate::contact::{normalize_name, Contact, Modifier, Origin};
+use crate::contact::{normalize_name, Contact, ContactId, Modifier, Origin};
 use crate::context::Context;
 use crate::dc_tools::time;
 use crate::events::EventType;
@@ -224,7 +224,7 @@ impl Job {
     async fn get_additional_mdn_jobs(
         &self,
         context: &Context,
-        contact_id: u32,
+        contact_id: ContactId,
     ) -> Result<(Vec<u32>, Vec<String>)> {
         // Extract message IDs from job parameters
         let res: Vec<(u32, MsgId)> = context
@@ -271,7 +271,7 @@ impl Job {
             return Status::Finished(Err(format_err!("MDNs are disabled")));
         }
 
-        let contact_id = self.foreign_id;
+        let contact_id = ContactId::new(self.foreign_id);
         let contact = job_try!(Contact::load_from_db(context, contact_id).await);
         if contact.is_blocked() {
             return Status::Finished(Err(format_err!("Contact is blocked")));
@@ -685,7 +685,11 @@ async fn send_mdn(context: &Context, msg: &Message) -> Result<()> {
     let mut param = Params::new();
     param.set(Param::MsgId, msg.id.to_u32().to_string());
 
-    add(context, Job::new(Action::SendMdn, msg.from_id, param, 0)).await?;
+    add(
+        context,
+        Job::new(Action::SendMdn, msg.from_id.to_u32(), param, 0),
+    )
+    .await?;
 
     Ok(())
 }
diff --git a/src/location.rs b/src/location.rs
index 6f1505a78..b092c750a 100644
--- a/src/location.rs
+++ b/src/location.rs
@@ -8,6 +8,7 @@ use quick_xml::events::{BytesEnd, BytesStart, BytesText};
 use crate::chat::{self, ChatId};
 use crate::config::Config;
 use crate::constants::{Viewtype, DC_CONTACT_ID_SELF};
+use crate::contact::ContactId;
 use crate::context::Context;
 use crate::dc_tools::time;
 use crate::events::EventType;
@@ -25,7 +26,7 @@ pub struct Location {
     pub longitude: f64,
     pub accuracy: f64,
     pub timestamp: i64,
-    pub contact_id: u32,
+    pub contact_id: ContactId,
     pub msg_id: u32,
     pub chat_id: ChatId,
     pub marker: Option<String>,
@@ -558,7 +559,7 @@ pub async fn set_msg_location_id(context: &Context, msg_id: MsgId, location_id:
 pub(crate) async fn save(
     context: &Context,
     chat_id: ChatId,
-    contact_id: u32,
+    contact_id: ContactId,
     locations: &[Location],
     independent: bool,
 ) -> Result<Option<u32>> {
@@ -585,12 +586,12 @@ pub(crate) async fn save(
             conn.prepare_cached("SELECT id FROM locations WHERE timestamp=? AND from_id=?")?;
         let mut stmt_insert = conn.prepare_cached(stmt_insert)?;
 
-        let exists = stmt_test.exists(paramsv![timestamp, contact_id as i32])?;
+        let exists = stmt_test.exists(paramsv![timestamp, contact_id])?;
 
         if independent || !exists {
             stmt_insert.execute(paramsv![
                 timestamp,
-                contact_id as i32,
+                contact_id,
                 chat_id,
                 latitude,
                 longitude,
diff --git a/src/message.rs b/src/message.rs
index d8d672c33..736e5f2bb 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -1,7 +1,6 @@
 //! # Messages and their identifiers.
 
 use std::collections::BTreeSet;
-use std::convert::TryInto;
 
 use anyhow::{ensure, format_err, Context as _, Result};
 use async_std::path::{Path, PathBuf};
@@ -14,7 +13,7 @@ use crate::constants::{
     Blocked, Chattype, VideochatType, Viewtype, DC_CHAT_ID_TRASH, DC_CONTACT_ID_INFO,
     DC_CONTACT_ID_SELF, DC_DESIRED_TEXT_LEN, DC_MSG_ID_LAST_SPECIAL,
 };
-use crate::contact::{Contact, Origin};
+use crate::contact::{Contact, ContactId, Origin};
 use crate::context::Context;
 use crate::dc_tools::{
     dc_create_smeared_timestamp, dc_get_filebytes, dc_get_filemeta, dc_gm2local_offset,
@@ -240,8 +239,8 @@ impl Default for MessengerMessage {
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
 pub struct Message {
     pub(crate) id: MsgId,
-    pub(crate) from_id: u32,
-    pub(crate) to_id: u32,
+    pub(crate) from_id: ContactId,
+    pub(crate) to_id: ContactId,
     pub(crate) chat_id: ChatId,
     pub(crate) viewtype: Viewtype,
     pub(crate) state: MessageState,
@@ -456,7 +455,7 @@ impl Message {
         self.id
     }
 
-    pub fn get_from_id(&self) -> u32 {
+    pub fn get_from_id(&self) -> ContactId {
         self.from_id
     }
 
@@ -1049,7 +1048,7 @@ pub async fn get_msg_info(context: &Context, msg_id: MsgId) -> Result<String> {
             "SELECT contact_id, timestamp_sent FROM msgs_mdns WHERE msg_id=?;",
             paramsv![msg_id],
             |row| {
-                let contact_id: i32 = row.get(0)?;
+                let contact_id: ContactId = row.get(0)?;
                 let ts: i64 = row.get(1)?;
                 Ok((contact_id, ts))
             },
@@ -1061,7 +1060,7 @@ pub async fn get_msg_info(context: &Context, msg_id: MsgId) -> Result<String> {
             let fts = dc_timestamp_to_str(ts);
             ret += &format!("Read: {}", fts);
 
-            let name = Contact::load_from_db(context, contact_id.try_into()?)
+            let name = Contact::load_from_db(context, contact_id)
                 .await
                 .map(|contact| contact.get_name_n_addr())
                 .unwrap_or_default();
@@ -1426,7 +1425,7 @@ pub async fn set_msg_failed(context: &Context, msg_id: MsgId, error: Option<impl
 /// returns Some if an event should be send
 pub async fn handle_mdn(
     context: &Context,
-    from_id: u32,
+    from_id: ContactId,
     rfc724_mid: &str,
     timestamp_sent: i64,
 ) -> Result<Option<(ChatId, MsgId)>> {
@@ -1479,7 +1478,7 @@ pub async fn handle_mdn(
         .sql
         .exists(
             "SELECT COUNT(*) FROM msgs_mdns WHERE msg_id=? AND contact_id=?;",
-            paramsv![msg_id, from_id as i32,],
+            paramsv![msg_id, from_id],
         )
         .await?
     {
@@ -1487,7 +1486,7 @@ pub async fn handle_mdn(
             .sql
             .execute(
                 "INSERT INTO msgs_mdns (msg_id, contact_id, timestamp_sent) VALUES (?, ?, ?);",
-                paramsv![msg_id, from_id as i32, timestamp_sent],
+                paramsv![msg_id, from_id, timestamp_sent],
             )
             .await?;
     }
diff --git a/src/mimeparser.rs b/src/mimeparser.rs
index 8b23c552d..9fd126586 100644
--- a/src/mimeparser.rs
+++ b/src/mimeparser.rs
@@ -13,7 +13,7 @@ use once_cell::sync::Lazy;
 use crate::aheader::Aheader;
 use crate::blob::BlobObject;
 use crate::constants::{Viewtype, DC_DESIRED_TEXT_LEN, DC_ELLIPSIS};
-use crate::contact::addr_normalize;
+use crate::contact::{addr_normalize, ContactId};
 use crate::context::Context;
 use crate::dc_tools::{dc_get_filemeta, dc_truncate, parse_receive_headers};
 use crate::dehtml::dehtml;
@@ -1369,7 +1369,7 @@ impl MimeMessage {
     pub async fn handle_reports(
         &self,
         context: &Context,
-        from_id: u32,
+        from_id: ContactId,
         sent_timestamp: i64,
         parts: &[Part],
     ) {
diff --git a/src/qr.rs b/src/qr.rs
index a0e669b26..5edbd9588 100644
--- a/src/qr.rs
+++ b/src/qr.rs
@@ -9,7 +9,7 @@ use std::collections::BTreeMap;
 use crate::chat::{self, get_chat_id_by_grpid, ChatIdBlocked};
 use crate::config::Config;
 use crate::constants::Blocked;
-use crate::contact::{addr_normalize, may_be_valid_addr, Contact, Origin};
+use crate::contact::{addr_normalize, may_be_valid_addr, Contact, ContactId, Origin};
 use crate::context::Context;
 use crate::dc_tools::time;
 use crate::key::Fingerprint;
@@ -30,7 +30,7 @@ const HTTPS_SCHEME: &str = "https://";
 #[derive(Debug, Clone, PartialEq)]
 pub enum Qr {
     AskVerifyContact {
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
@@ -38,16 +38,16 @@ pub enum Qr {
     AskVerifyGroup {
         grpname: String,
         grpid: String,
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
     },
     FprOk {
-        contact_id: u32,
+        contact_id: ContactId,
     },
     FprMismatch {
-        contact_id: Option<u32>,
+        contact_id: Option<ContactId>,
     },
     FprWithoutAddr {
         fingerprint: String,
@@ -60,7 +60,7 @@ pub enum Qr {
         instance_pattern: String,
     },
     Addr {
-        contact_id: u32,
+        contact_id: ContactId,
     },
     Url {
         url: String,
@@ -69,7 +69,7 @@ pub enum Qr {
         text: String,
     },
     WithdrawVerifyContact {
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
@@ -77,13 +77,13 @@ pub enum Qr {
     WithdrawVerifyGroup {
         grpname: String,
         grpid: String,
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
     },
     ReviveVerifyContact {
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
@@ -91,7 +91,7 @@ pub enum Qr {
     ReviveVerifyGroup {
         grpname: String,
         grpid: String,
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
@@ -711,7 +711,7 @@ mod tests {
             ..
         } = qr
         {
-            assert_ne!(contact_id, 0);
+            assert_ne!(contact_id, ContactId::new(0));
             assert_eq!(grpname, "test ? test !");
         } else {
             bail!("Wrong QR code type");
@@ -729,7 +729,7 @@ mod tests {
             ..
         } = qr
         {
-            assert_ne!(contact_id, 0);
+            assert_ne!(contact_id, ContactId::new(0));
             assert_eq!(grpname, "test ? test !");
 
             let contact = Contact::get_by_id(&ctx.ctx, contact_id).await?;
@@ -751,7 +751,7 @@ mod tests {
         ).await?;
 
         if let Qr::AskVerifyContact { contact_id, .. } = qr {
-            assert_ne!(contact_id, 0);
+            assert_ne!(contact_id, ContactId::new(0));
         } else {
             bail!("Wrong QR code type");
         }
diff --git a/src/securejoin.rs b/src/securejoin.rs
index a4d76dbeb..0c2e821a0 100644
--- a/src/securejoin.rs
+++ b/src/securejoin.rs
@@ -9,7 +9,7 @@ use crate::aheader::EncryptPreference;
 use crate::chat::{self, Chat, ChatId, ChatIdBlocked};
 use crate::config::Config;
 use crate::constants::{Blocked, Viewtype, DC_CONTACT_ID_LAST_SPECIAL};
-use crate::contact::{Contact, Origin, VerifiedStatus};
+use crate::contact::{Contact, ContactId, Origin, VerifiedStatus};
 use crate::context::Context;
 use crate::dc_tools::time;
 use crate::e2ee::ensure_secret_key_exists;
@@ -205,7 +205,7 @@ pub struct SendMsgError(#[from] anyhow::Error);
 /// Bob's handshake messages are sent in `BobState::send_handshake_message()`.
 async fn send_alice_handshake_msg(
     context: &Context,
-    contact_id: u32,
+    contact_id: ContactId,
     step: &str,
     fingerprint: Option<Fingerprint>,
 ) -> Result<(), SendMsgError> {
@@ -233,7 +233,7 @@ async fn send_alice_handshake_msg(
 }
 
 /// Get an unblocked chat that can be used for info messages.
-async fn info_chat_id(context: &Context, contact_id: u32) -> Result<ChatId> {
+async fn info_chat_id(context: &Context, contact_id: ContactId) -> Result<ChatId> {
     let chat_id_blocked = ChatIdBlocked::get_for_contact(context, contact_id, Blocked::Not).await?;
     Ok(chat_id_blocked.id)
 }
@@ -241,7 +241,7 @@ async fn info_chat_id(context: &Context, contact_id: u32) -> Result<ChatId> {
 async fn fingerprint_equals_sender(
     context: &Context,
     fingerprint: &Fingerprint,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<bool, Error> {
     let contact = Contact::load_from_db(context, contact_id).await?;
     let peerstate = match Peerstate::from_addr(context, contact.get_addr()).await {
@@ -308,7 +308,7 @@ pub(crate) enum HandshakeMessage {
 pub(crate) async fn handle_securejoin_handshake(
     context: &Context,
     mime_message: &MimeMessage,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<HandshakeMessage> {
     if contact_id <= DC_CONTACT_ID_LAST_SPECIAL {
         return Err(Error::msg("Can not be called with special contact ID"));
@@ -571,7 +571,7 @@ pub(crate) async fn handle_securejoin_handshake(
 pub(crate) async fn observe_securejoin_on_other_device(
     context: &Context,
     mime_message: &MimeMessage,
-    contact_id: u32,
+    contact_id: ContactId,
 ) -> Result<HandshakeMessage> {
     if contact_id <= DC_CONTACT_ID_LAST_SPECIAL {
         return Err(Error::msg("Can not be called with special contact ID"));
@@ -636,7 +636,7 @@ pub(crate) async fn observe_securejoin_on_other_device(
 
 async fn secure_connection_established(
     context: &Context,
-    contact_id: u32,
+    contact_id: ContactId,
     chat_id: ChatId,
 ) -> Result<(), Error> {
     let contact = Contact::get_by_id(context, contact_id).await?;
@@ -648,7 +648,7 @@ async fn secure_connection_established(
 
 async fn could_not_establish_secure_connection(
     context: &Context,
-    contact_id: u32,
+    contact_id: ContactId,
     chat_id: ChatId,
     details: &str,
 ) -> Result<(), Error> {
diff --git a/src/securejoin/qrinvite.rs b/src/securejoin/qrinvite.rs
index 9e25a6159..4f961e78e 100644
--- a/src/securejoin/qrinvite.rs
+++ b/src/securejoin/qrinvite.rs
@@ -8,6 +8,7 @@ use std::convert::TryFrom;
 
 use anyhow::{bail, Error, Result};
 
+use crate::contact::ContactId;
 use crate::key::Fingerprint;
 use crate::qr::Qr;
 
@@ -17,13 +18,13 @@ use crate::qr::Qr;
 #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
 pub enum QrInvite {
     Contact {
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         invitenumber: String,
         authcode: String,
     },
     Group {
-        contact_id: u32,
+        contact_id: ContactId,
         fingerprint: Fingerprint,
         name: String,
         grpid: String,
@@ -37,7 +38,7 @@ impl QrInvite {
     ///
     /// The actual QR-code contains a URL-encoded email address, but upon scanning this is
     /// translated to a contact ID.
-    pub fn contact_id(&self) -> u32 {
+    pub fn contact_id(&self) -> ContactId {
         match self {
             Self::Contact { contact_id, .. } | Self::Group { contact_id, .. } => *contact_id,
         }
diff --git a/src/stock_str.rs b/src/stock_str.rs
index eabdc0260..c6299b377 100644
--- a/src/stock_str.rs
+++ b/src/stock_str.rs
@@ -11,7 +11,7 @@ use crate::blob::BlobObject;
 use crate::chat::{self, Chat, ChatId, ProtectionStatus};
 use crate::config::Config;
 use crate::constants::{Viewtype, DC_CONTACT_ID_SELF};
-use crate::contact::{Contact, Origin};
+use crate::contact::{Contact, ContactId, Origin};
 use crate::context::Context;
 use crate::dc_tools::dc_timestamp_to_str;
 use crate::message::Message;
@@ -389,7 +389,7 @@ trait StockStringMods: AsRef<str> + Sized {
     fn action_by_contact<'a>(
         self,
         context: &'a Context,
-        contact_id: u32,
+        contact_id: ContactId,
     ) -> Pin<Box<dyn Future<Output = String> + Send + 'a>>
     where
         Self: Send + 'a,
@@ -457,7 +457,7 @@ pub(crate) async fn msg_grp_name(
     context: &Context,
     from_group: impl AsRef<str>,
     to_group: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     translated(context, StockMessage::MsgGrpName)
         .await
@@ -468,7 +468,7 @@ pub(crate) async fn msg_grp_name(
 }
 
 /// Stock string: `Group image changed.`.
-pub(crate) async fn msg_grp_img_changed(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_grp_img_changed(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgGrpImgChanged)
         .await
         .action_by_contact(context, by_contact)
@@ -482,7 +482,7 @@ pub(crate) async fn msg_grp_img_changed(context: &Context, by_contact: u32) -> S
 pub(crate) async fn msg_add_member(
     context: &Context,
     added_member_addr: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     let addr = added_member_addr.as_ref();
     let who = match Contact::lookup_id_by_addr(context, addr, Origin::Unknown).await {
@@ -506,7 +506,7 @@ pub(crate) async fn msg_add_member(
 pub(crate) async fn msg_del_member(
     context: &Context,
     removed_member_addr: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     let addr = removed_member_addr.as_ref();
     let who = match Contact::lookup_id_by_addr(context, addr, Origin::Unknown).await {
@@ -524,7 +524,7 @@ pub(crate) async fn msg_del_member(
 }
 
 /// Stock string: `Group left.`.
-pub(crate) async fn msg_group_left(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_group_left(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgGroupLeft)
         .await
         .action_by_contact(context, by_contact)
@@ -574,7 +574,7 @@ pub(crate) async fn read_rcpt_mail_body(context: &Context, message: impl AsRef<s
 }
 
 /// Stock string: `Group image deleted.`.
-pub(crate) async fn msg_grp_img_deleted(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_grp_img_deleted(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgGrpImgDeleted)
         .await
         .action_by_contact(context, by_contact)
@@ -587,7 +587,10 @@ pub(crate) async fn e2e_preferred(context: &Context) -> String {
 }
 
 /// Stock string: `%1$s invited you to join this group. Waiting for the device of %2$s to reply…`.
-pub(crate) async fn secure_join_started(context: &Context, inviter_contact_id: u32) -> String {
+pub(crate) async fn secure_join_started(
+    context: &Context,
+    inviter_contact_id: ContactId,
+) -> String {
     if let Ok(contact) = Contact::get_by_id(context, inviter_contact_id).await {
         translated(context, StockMessage::SecureJoinStarted)
             .await
@@ -602,7 +605,7 @@ pub(crate) async fn secure_join_started(context: &Context, inviter_contact_id: u
 }
 
 /// Stock string: `%1$s replied, waiting for being added to the group…`.
-pub(crate) async fn secure_join_replies(context: &Context, contact_id: u32) -> String {
+pub(crate) async fn secure_join_replies(context: &Context, contact_id: ContactId) -> String {
     if let Ok(contact) = Contact::get_by_id(context, contact_id).await {
         translated(context, StockMessage::SecureJoinReplies)
             .await
@@ -718,7 +721,7 @@ pub(crate) async fn msg_location_enabled(context: &Context) -> String {
 }
 
 /// Stock string: `Location streaming enabled by ...`.
-pub(crate) async fn msg_location_enabled_by(context: &Context, contact: u32) -> String {
+pub(crate) async fn msg_location_enabled_by(context: &Context, contact: ContactId) -> String {
     translated(context, StockMessage::MsgLocationEnabled)
         .await
         .action_by_contact(context, contact)
@@ -784,7 +787,10 @@ pub(crate) async fn failed_sending_to(context: &Context, name: impl AsRef<str>)
 }
 
 /// Stock string: `Message deletion timer is disabled.`.
-pub(crate) async fn msg_ephemeral_timer_disabled(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_ephemeral_timer_disabled(
+    context: &Context,
+    by_contact: ContactId,
+) -> String {
     translated(context, StockMessage::MsgEphemeralTimerDisabled)
         .await
         .action_by_contact(context, by_contact)
@@ -795,7 +801,7 @@ pub(crate) async fn msg_ephemeral_timer_disabled(context: &Context, by_contact:
 pub(crate) async fn msg_ephemeral_timer_enabled(
     context: &Context,
     timer: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     translated(context, StockMessage::MsgEphemeralTimerEnabled)
         .await
@@ -805,7 +811,7 @@ pub(crate) async fn msg_ephemeral_timer_enabled(
 }
 
 /// Stock string: `Message deletion timer is set to 1 minute.`.
-pub(crate) async fn msg_ephemeral_timer_minute(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_ephemeral_timer_minute(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgEphemeralTimerMinute)
         .await
         .action_by_contact(context, by_contact)
@@ -813,7 +819,7 @@ pub(crate) async fn msg_ephemeral_timer_minute(context: &Context, by_contact: u3
 }
 
 /// Stock string: `Message deletion timer is set to 1 hour.`.
-pub(crate) async fn msg_ephemeral_timer_hour(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_ephemeral_timer_hour(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgEphemeralTimerHour)
         .await
         .action_by_contact(context, by_contact)
@@ -821,7 +827,7 @@ pub(crate) async fn msg_ephemeral_timer_hour(context: &Context, by_contact: u32)
 }
 
 /// Stock string: `Message deletion timer is set to 1 day.`.
-pub(crate) async fn msg_ephemeral_timer_day(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_ephemeral_timer_day(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgEphemeralTimerDay)
         .await
         .action_by_contact(context, by_contact)
@@ -829,7 +835,7 @@ pub(crate) async fn msg_ephemeral_timer_day(context: &Context, by_contact: u32)
 }
 
 /// Stock string: `Message deletion timer is set to 1 week.`.
-pub(crate) async fn msg_ephemeral_timer_week(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn msg_ephemeral_timer_week(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::MsgEphemeralTimerWeek)
         .await
         .action_by_contact(context, by_contact)
@@ -874,7 +880,7 @@ pub(crate) async fn error_no_network(context: &Context) -> String {
 }
 
 /// Stock string: `Chat protection enabled.`.
-pub(crate) async fn protection_enabled(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn protection_enabled(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::ProtectionEnabled)
         .await
         .action_by_contact(context, by_contact)
@@ -882,7 +888,7 @@ pub(crate) async fn protection_enabled(context: &Context, by_contact: u32) -> St
 }
 
 /// Stock string: `Chat protection disabled.`.
-pub(crate) async fn protection_disabled(context: &Context, by_contact: u32) -> String {
+pub(crate) async fn protection_disabled(context: &Context, by_contact: ContactId) -> String {
     translated(context, StockMessage::ProtectionDisabled)
         .await
         .action_by_contact(context, by_contact)
@@ -908,7 +914,7 @@ pub(crate) async fn delete_server_turned_off(context: &Context) -> String {
 pub(crate) async fn msg_ephemeral_timer_minutes(
     context: &Context,
     minutes: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     translated(context, StockMessage::MsgEphemeralTimerMinutes)
         .await
@@ -921,7 +927,7 @@ pub(crate) async fn msg_ephemeral_timer_minutes(
 pub(crate) async fn msg_ephemeral_timer_hours(
     context: &Context,
     hours: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     translated(context, StockMessage::MsgEphemeralTimerHours)
         .await
@@ -934,7 +940,7 @@ pub(crate) async fn msg_ephemeral_timer_hours(
 pub(crate) async fn msg_ephemeral_timer_days(
     context: &Context,
     days: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     translated(context, StockMessage::MsgEphemeralTimerDays)
         .await
@@ -947,7 +953,7 @@ pub(crate) async fn msg_ephemeral_timer_days(
 pub(crate) async fn msg_ephemeral_timer_weeks(
     context: &Context,
     weeks: impl AsRef<str>,
-    by_contact: u32,
+    by_contact: ContactId,
 ) -> String {
     translated(context, StockMessage::MsgEphemeralTimerWeeks)
         .await
@@ -1104,7 +1110,7 @@ impl Context {
     pub(crate) async fn stock_protection_msg(
         &self,
         protect: ProtectionStatus,
-        from_id: u32,
+        from_id: ContactId,
     ) -> String {
         match protect {
             ProtectionStatus::Unprotected => protection_enabled(self, from_id).await,
diff --git a/src/test_utils.rs b/src/test_utils.rs
index 110a211da..feeaf6be0 100644
--- a/src/test_utils.rs
+++ b/src/test_utils.rs
@@ -851,7 +851,7 @@ async fn log_msg(context: &Context, prefix: impl AsRef<str>, msg: &Message) {
         &contact_name,
         contact_id,
         msgtext.unwrap_or_default(),
-        if msg.get_from_id() == 1u32 {
+        if msg.get_from_id() == DC_CONTACT_ID_SELF {
             ""
         } else if msg.get_state() == MessageState::InSeen {
             "[SEEN]"
diff --git a/src/update_helper.rs b/src/update_helper.rs
index 2e200e5dc..3dc1629ef 100644
--- a/src/update_helper.rs
+++ b/src/update_helper.rs
@@ -1,7 +1,7 @@
 //! # Functions to update timestamps.
 
 use crate::chat::{Chat, ChatId};
-use crate::contact::Contact;
+use crate::contact::{Contact, ContactId};
 use crate::context::Context;
 use crate::param::{Param, Params};
 use anyhow::Result;
@@ -12,7 +12,7 @@ impl Context {
     /// (if we have a ContactId type at some point, the function should go there)
     pub(crate) async fn update_contacts_timestamp(
         &self,
-        contact_id: u32,
+        contact_id: ContactId,
         scope: Param,
         new_timestamp: i64,
     ) -> Result<bool> {