move smtp-send chunking from chat.rs to smtp loop and use max-recipients value for the smtp transport in use, add chunking tests

deltachat-ffi/src/lib.rs

@@ -275,7 +275,7 @@ pub unsafe extern "C" fn dc_get_config(
                 .strdup()
         } else {
             match config::Config::from_str(&key)
-                .with_context(|| format!("Invalid key {key:?}"))
+                .with_context(|| format!("Invalid key {:?}", &key))
                 .log_err(ctx)
             {
                 Ok(key) => ctx

deltachat-repl/src/cmdline.rs

@@ -122,7 +122,7 @@ async fn poke_spec(context: &Context, spec: Option<&str>) -> bool {
                 let name_f = entry.file_name();
                 let name = name_f.to_string_lossy();
                 if name.ends_with(".eml") {
-                    let path_plus_name = format!("{real_spec}/{name}");
+                    let path_plus_name = format!("{}/{}", &real_spec, name);
                     println!("Import: {path_plus_name}");
                     if poke_eml_file(context, Path::new(&path_plus_name))
                         .await
@@ -133,11 +133,11 @@ async fn poke_spec(context: &Context, spec: Option<&str>) -> bool {
                 }
             }
         } else {
-            eprintln!("Import: Cannot open directory {real_spec:?}.");
+            eprintln!("Import: Cannot open directory \"{}\".", &real_spec);
             return false;
         }
     }
-    println!("Import: {read_cnt} items read from {real_spec:?}.");
+    println!("Import: {} items read from \"{}\".", read_cnt, &real_spec);
     if read_cnt > 0 {
         context.emit_msgs_changed_without_ids();
     }
@@ -179,7 +179,7 @@ async fn log_msg(context: &Context, prefix: impl AsRef<str>, msg: &Message) {
         msg.get_id(),
         if msg.get_showpadlock() { "🔒" } else { "" },
         if msg.has_location() { "📍" } else { "" },
-        contact_name,
+        &contact_name,
         contact_id,
         msgtext,
         if msg.has_html() { "[HAS-HTML]️" } else { "" },
@@ -221,7 +221,7 @@ async fn log_msg(context: &Context, prefix: impl AsRef<str>, msg: &Message) {
         },
         statestr,
         downloadstate,
-        temp2,
+        &temp2,
     );
 }
 
@@ -561,7 +561,7 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
                             .map_or_else(String::new, |prefix| format!("{prefix}: ")),
                         summary.text,
                         statestr,
-                        timestr,
+                        &timestr,
                         if chat.is_sending_locations() {
                             "📍"
                         } else {

deltachat-repl/src/main.rs

@@ -432,7 +432,7 @@ async fn handle_cmd(
                 {
                     println!("Open the following url, set mail_pw to the generated token and server_flags to 2:\n{oauth2_url}");
                 } else {
-                    println!("OAuth2 not available for {addr}.");
+                    println!("OAuth2 not available for {}.", &addr);
                 }
             } else {
                 println!("oauth2: set addr first.");

src/accounts.rs

@@ -794,7 +794,7 @@ impl Config {
                 .with_push_subscriber(push_subscriber.clone())
                 .build()
                 .await
-                .with_context(|| format!("failed to create context from file {dbfile:?}"))?;
+                .with_context(|| format!("failed to create context from file {:?}", &dbfile))?;
             // Try to open without a passphrase,
             // but do not return an error if account is passphare-protected.
             ctx.open("".to_string()).await?;

src/chat.rs

@@ -2529,7 +2529,7 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
         // running numbers, etc.
         let filename: String = match viewtype_orig {
             Viewtype::Voice => format!(
-                "voice-messsage_{}.{suffix}",
+                "voice-messsage_{}.{}",
                 chrono::Utc
                     .timestamp_opt(msg.timestamp_sort, 0)
                     .single()
@@ -2537,9 +2537,10 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
                         || "YY-mm-dd_hh:mm:ss".to_string(),
                         |ts| ts.format("%Y-%m-%d_%H-%M-%S").to_string()
                     ),
+                &suffix
             ),
             Viewtype::Image | Viewtype::Gif => format!(
-                "image_{}.{suffix}",
+                "image_{}.{}",
                 chrono::Utc
                     .timestamp_opt(msg.timestamp_sort, 0)
                     .single()
@@ -2547,9 +2548,10 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
                         || "YY-mm-dd_hh:mm:ss".to_string(),
                         |ts| ts.format("%Y-%m-%d_%H-%M-%S").to_string(),
                     ),
+                &suffix,
             ),
             Viewtype::Video => format!(
-                "video_{}.{suffix}",
+                "video_{}.{}",
                 chrono::Utc
                     .timestamp_opt(msg.timestamp_sort, 0)
                     .single()
@@ -2557,6 +2559,7 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
                         || "YY-mm-dd_hh:mm:ss".to_string(),
                         |ts| ts.format("%Y-%m-%d_%H-%M-%S").to_string()
                     ),
+                &suffix
             ),
             _ => filename,
         };
@@ -2951,7 +2954,6 @@ WHERE id=?
         )
         .await?;
 
-    let chunk_size = context.get_max_smtp_rcpt_to().await?;
     let trans_fn = |t: &mut rusqlite::Transaction| {
         let mut row_ids = Vec::<i64>::new();
 
@@ -2965,12 +2967,12 @@ WHERE id=?
             "INSERT INTO smtp (rfc724_mid, recipients, mime, msg_id)
             VALUES            (?1,         ?2,         ?3,   ?4)",
         )?;
-        for recipients_chunk in recipients.chunks(chunk_size) {
-            let recipients_chunk = recipients_chunk.join(" ");
+        if !recipients.is_empty() {
+            let all_recipients = recipients.join(" ");
             if let Some(pre_msg) = &rendered_pre_msg {
                 let row_id = stmt.execute((
                     &pre_msg.rfc724_mid,
-                    &recipients_chunk,
+                    &all_recipients,
                     &pre_msg.message,
                     msg.id,
                 ))?;
@@ -2978,7 +2980,7 @@ WHERE id=?
             }
             let row_id = stmt.execute((
                 &rendered_msg.rfc724_mid,
-                &recipients_chunk,
+                &all_recipients,
                 &rendered_msg.message,
                 msg.id,
             ))?;

src/configure.rs

@@ -707,7 +707,8 @@ async fn get_autoconfig(
         ctx,
         // the doc does not mention `emailaddress=`, however, Thunderbird adds it, see <https://releases.mozilla.org/pub/thunderbird/>,  which makes some sense
         &format!(
-            "https://{param_domain}/.well-known/autoconfig/mail/config-v1.1.xml?emailaddress={param_addr_urlencoded}"
+            "https://{}/.well-known/autoconfig/mail/config-v1.1.xml?emailaddress={}",
+            &param_domain, &param_addr_urlencoded
         ),
         &param.addr,
     )
@@ -720,7 +721,7 @@ async fn get_autoconfig(
     // Outlook uses always SSL but different domains (this comment describes the next two steps)
     if let Ok(res) = outlk_autodiscover(
         ctx,
-        format!("https://{param_domain}/autodiscover/autodiscover.xml"),
+        format!("https://{}/autodiscover/autodiscover.xml", &param_domain),
     )
     .await
     {
@@ -730,7 +731,10 @@ async fn get_autoconfig(
 
     if let Ok(res) = outlk_autodiscover(
         ctx,
-        format!("https://autodiscover.{param_domain}/autodiscover/autodiscover.xml",),
+        format!(
+            "https://autodiscover.{}/autodiscover/autodiscover.xml",
+            &param_domain
+        ),
     )
     .await
     {
@@ -741,7 +745,7 @@ async fn get_autoconfig(
     // always SSL for Thunderbird's database
     if let Ok(res) = moz_autoconfigure(
         ctx,
-        &format!("https://autoconfig.thunderbird.net/v1.1/{param_domain}"),
+        &format!("https://autoconfig.thunderbird.net/v1.1/{}", &param_domain),
         &param.addr,
     )
     .await

src/constants.rs

@@ -204,9 +204,6 @@ pub const MAX_RCVD_IMAGE_PIXELS: u32 = 50_000_000;
 // `max_smtp_rcpt_to` in the provider db.
 pub(crate) const DEFAULT_MAX_SMTP_RCPT_TO: usize = 50;
 
-/// Same as `DEFAULT_MAX_SMTP_RCPT_TO`, but for chatmail relays.
-pub(crate) const DEFAULT_CHATMAIL_MAX_SMTP_RCPT_TO: usize = 999;
-
 /// How far the last quota check needs to be in the past to be checked by the background function (in seconds).
 pub(crate) const DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT: u64 = 12 * 60 * 60; // 12 hours
 

src/context.rs

@@ -16,7 +16,7 @@ use tokio::sync::{Mutex, Notify, RwLock};
 
 use crate::chat::{ChatId, get_chat_cnt};
 use crate::config::Config;
-use crate::constants::{self, DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT, DC_VERSION_STR};
+use crate::constants::{DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT, DC_VERSION_STR};
 use crate::contact::{Contact, ContactId};
 use crate::debug_logging::DebugLogging;
 use crate::events::{Event, EventEmitter, EventType, Events};
@@ -587,23 +587,6 @@ impl Context {
         self.get_config_bool(Config::IsChatmail).await
     }
 
-    /// Returns maximum number of recipients the provider allows to send a single email to.
-    pub(crate) async fn get_max_smtp_rcpt_to(&self) -> Result<usize> {
-        let is_chatmail = self.is_chatmail().await?;
-        let val = self
-            .get_configured_provider()
-            .await?
-            .and_then(|provider| provider.opt.max_smtp_rcpt_to)
-            .map_or_else(
-                || match is_chatmail {
-                    true => constants::DEFAULT_CHATMAIL_MAX_SMTP_RCPT_TO,
-                    false => constants::DEFAULT_MAX_SMTP_RCPT_TO,
-                },
-                usize::from,
-            );
-        Ok(val)
-    }
-
     /// Does a single round of fetching from IMAP and returns.
     ///
     /// Can be used even if I/O is currently stopped.

src/imap.rs

@@ -1045,12 +1045,15 @@ impl Session {
             if target.is_empty() {
                 self.delete_message_batch(context, &uid_set, rowid_set)
                     .await
-                    .with_context(|| format!("cannot delete batch of messages {uid_set:?}"))?;
+                    .with_context(|| format!("cannot delete batch of messages {:?}", &uid_set))?;
             } else {
                 self.move_message_batch(context, &uid_set, rowid_set, &target)
                     .await
                     .with_context(|| {
-                        format!("cannot move batch of messages {uid_set:?} to folder {target:?}",)
+                        format!(
+                            "cannot move batch of messages {:?} to folder {:?}",
+                            &uid_set, target
+                        )
                     })?;
             }
         }
@@ -1284,10 +1287,9 @@ impl Session {
 
         for (request_uids, set) in build_sequence_sets(&request_uids)? {
             info!(context, "Starting UID FETCH of message set \"{}\".", set);
-            let mut fetch_responses = self
-                .uid_fetch(&set, BODY_FULL)
-                .await
-                .with_context(|| format!("fetching messages {set} from folder {folder:?}"))?;
+            let mut fetch_responses = self.uid_fetch(&set, BODY_FULL).await.with_context(|| {
+                format!("fetching messages {} from folder \"{}\"", &set, folder)
+            })?;
 
             // Map from UIDs to unprocessed FETCH results. We put unprocessed FETCH results here
             // when we want to process other messages first.
@@ -1501,7 +1503,7 @@ impl Session {
             .get_metadata(
                 mailbox,
                 options,
-                "(/shared/comment /shared/admin /shared/vendor/deltachat/irohrelay /shared/vendor/deltachat/turn)",
+                "(/shared/comment /shared/admin /shared/vendor/deltachat/irohrelay /shared/vendor/deltachat/turn /shared/vendor/deltachat/maxsmtprecipients)",
             )
             .await?;
         for m in metadata {
@@ -1537,6 +1539,21 @@ impl Session {
                         }
                     }
                 }
+                "/shared/vendor/deltachat/maxsmtprecipients" => {
+                    if let Some(value) = m.value.and_then(|v| v.parse::<u32>().ok()) {
+                        let transport_id = self.transport_id();
+                        context
+                            .sql
+                            .execute(
+                                "UPDATE transports \
+                                 SET max_smtp_rcpt_to=? WHERE id=?",
+                                (value, transport_id),
+                            )
+                            .await
+                            .log_err(context)
+                            .ok();
+                    }
+                }
                 _ => {}
             }
         }

src/message.rs

@@ -222,7 +222,7 @@ SELECT ?1, rfc724_mid, pre_rfc724_mid, timestamp, ?, ? FROM msgs WHERE id=?1
             } else {
                 msg.timestamp_sort
             });
-            ret += &format!("Received: {s}");
+            ret += &format!("Received: {}", &s);
             ret += "\n";
         }
 
@@ -301,7 +301,7 @@ SELECT ?1, rfc724_mid, pre_rfc724_mid, timestamp, ?, ? FROM msgs WHERE id=?1
             ret += "Type: ";
             ret += &format!("{}", msg.viewtype);
             ret += "\n";
-            ret += &format!("Mimetype: {}\n", msg.get_filemime().unwrap_or_default());
+            ret += &format!("Mimetype: {}\n", &msg.get_filemime().unwrap_or_default());
         }
         let w = msg.param.get_int(Param::Width).unwrap_or_default();
         let h = msg.param.get_int(Param::Height).unwrap_or_default();

src/qr_code_generator.rs

@@ -332,7 +332,7 @@ fn inner_generate_secure_join_qr_code(
                 d.attr("cx", logo_position_x + HALF_LOGO_SIZE)?;
                 d.attr("cy", logo_position_y + HALF_LOGO_SIZE)?;
                 d.attr("r", HALF_LOGO_SIZE)?;
-                d.attr("style", format!("fill:{color}"))
+                d.attr("style", format!("fill:{}", &color))
             })?;
 
             let avatar_font_size = LOGO_SIZE * 0.65;

src/receive_imf.rs

@@ -3560,7 +3560,12 @@ async fn create_or_lookup_mailinglist_or_broadcast(
             mime_parser.timestamp_sent,
         )
         .await
-        .with_context(|| format!("failed to create mailinglist '{name}' for grpid={listid}",))?;
+        .with_context(|| {
+            format!(
+                "failed to create mailinglist '{}' for grpid={}",
+                &name, &listid
+            )
+        })?;
 
         if chattype == Chattype::InBroadcast {
             chat::add_to_chat_contacts_table(

src/scheduler/connectivity.rs

@@ -218,7 +218,7 @@ pub(crate) fn maybe_network_lost(context: &Context, stores: Vec<ConnectivityStor
 impl fmt::Debug for ConnectivityStore {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         if let Some(guard) = self.0.try_lock() {
-            write!(f, "ConnectivityStore {:?}", *guard)
+            write!(f, "ConnectivityStore {:?}", &*guard)
         } else {
             write!(f, "ConnectivityStore [LOCKED]")
         }

src/securejoin.rs

@@ -73,7 +73,8 @@ fn shorten_name(name: &str, length: usize) -> String {
         // We use _ rather than ... to avoid dots at the end of the URL, which would confuse linkifiers
         format!(
             "{}_",
-            name.chars()
+            &name
+                .chars()
                 .take(length.saturating_sub(1))
                 .collect::<String>()
         )

src/securejoin/securejoin_tests.rs

@@ -992,7 +992,7 @@ async fn test_wrong_auth_token() -> Result<()> {
     tcm.send_recv(alice, bob, "hi").await;
 
     let alice_qr = get_securejoin_qr(alice, None).await?;
-    println!("{alice_qr}");
+    println!("{}", &alice_qr);
     let invalid_alice_qr = alice_qr.replace("&s=", "&s=INVALIDAUTHTOKEN&someotherkey=");
 
     join_securejoin(bob, &invalid_alice_qr).await?;

src/smtp.rs

@@ -2,6 +2,8 @@
 
 mod connect;
 pub mod send;
+#[cfg(test)]
+mod chunking_tests;
 
 use anyhow::{Context as _, Error, Result, bail, format_err};
 use async_smtp::response::{Category, Code, Detail};
@@ -10,6 +12,7 @@ use tokio::task;
 
 use crate::chat::{ChatId, add_info_msg_with_cmd};
 use crate::config::Config;
+use crate::constants;
 use crate::contact::{Contact, ContactId};
 use crate::context::Context;
 use crate::events::EventType;
@@ -34,6 +37,9 @@ pub(crate) struct Smtp {
     /// Email address we are sending from.
     from: Option<EmailAddress>,
 
+    /// Transport used for the current connection.
+    transport_id: Option<u32>,
+
     /// Timestamp of last successful send/receive network interaction
     /// (eg connect or send succeeded). On initialization and disconnect
     /// it is set to None.
@@ -60,6 +66,7 @@ impl Smtp {
             task::spawn(async move { transport.quit().await });
         }
         self.last_success = None;
+        self.transport_id = None;
     }
 
     /// Return true if smtp was connected but is not known to
@@ -89,9 +96,10 @@ impl Smtp {
         }
 
         self.connectivity.set_connecting(context);
-        let (_transport_id, lp) = ConfiguredLoginParam::load(context)
+        let (transport_id, lp) = ConfiguredLoginParam::load(context)
             .await?
             .context("Not configured")?;
+        self.transport_id = Some(transport_id);
         let proxy_config = ProxyConfig::load(context).await?;
         self.connect(
             context,
@@ -165,6 +173,7 @@ impl Smtp {
     }
 }
 
+#[derive(Debug)]
 pub(crate) enum SendResult {
     /// Message was sent successfully.
     Success,
@@ -176,13 +185,36 @@ pub(crate) enum SendResult {
     Retry,
 }
 
+pub(crate) trait SmtpSender: Send {
+    fn send_chunk<'a>(
+        &'a mut self,
+        context: &'a Context,
+        recipients: &'a [async_smtp::EmailAddress],
+        body: &'a str,
+    ) -> futures::future::BoxFuture<'a, SendResult>;
+}
+
+struct RealSmtpSender<'a> {
+    smtp: &'a mut Smtp,
+}
+
+impl SmtpSender for RealSmtpSender<'_> {
+    fn send_chunk<'a>(
+        &'a mut self,
+        context: &'a Context,
+        recipients: &'a [async_smtp::EmailAddress],
+        body: &'a str,
+    ) -> futures::future::BoxFuture<'a, SendResult> {
+        Box::pin(smtp_send(context, recipients, body, self.smtp))
+    }
+}
+
 /// Tries to send a message.
 pub(crate) async fn smtp_send(
     context: &Context,
     recipients: &[async_smtp::EmailAddress],
     message: &str,
     smtp: &mut Smtp,
-    msg_id: Option<MsgId>,
 ) -> SendResult {
     if recipients.is_empty() {
         return SendResult::Success;
@@ -310,25 +342,6 @@ pub(crate) async fn smtp_send(
         Ok(()) => SendResult::Success,
     };
 
-    if let SendResult::Failure(err) = &status
-        && let Some(msg_id) = msg_id
-    {
-        // We couldn't send the message, so mark it as failed
-        match Message::load_from_db(context, msg_id).await {
-            Ok(mut msg) => {
-                if let Err(err) = message::set_msg_failed(context, &mut msg, &err.to_string()).await
-                {
-                    error!(context, "Failed to mark {msg_id} as failed: {err:#}.");
-                }
-            }
-            Err(err) => {
-                error!(
-                    context,
-                    "Failed to load {msg_id} to mark it as failed: {err:#}."
-                );
-            }
-        }
-    }
     status
 }
 
@@ -406,7 +419,40 @@ pub(crate) async fn send_msg_to_smtp(
         )
         .collect::<Vec<_>>();
 
-    let status = smtp_send(context, &recipients_list, body.as_str(), smtp, Some(msg_id)).await;
+    let transport_id = smtp
+        .transport_id
+        .context("SMTP not connected to a transport")?;
+    let chunk_size = max_smtp_rcpt_to(context, transport_id).await?;
+
+    let mut sender = RealSmtpSender { smtp };
+    let (status, start_idx) = send_smtp_chunks(
+        context,
+        &recipients_list,
+        body.as_str(),
+        chunk_size,
+        &mut sender,
+    )
+    .await;
+
+    let unsent_saved = start_idx < recipients_list.len();
+    if let Some(unsent) = recipients_list.get(start_idx..)
+        && !unsent.is_empty()
+    {
+        let unsent_str: String = unsent
+            .iter()
+            .map(|a| a.as_ref())
+            .collect::<Vec<&str>>()
+            .join(" ");
+        context
+            .sql
+            .execute(
+                "UPDATE smtp SET recipients=? WHERE id=?",
+                (unsent_str, rowid),
+            )
+            .await
+            .log_err(context)
+            .ok();
+    }
 
     match status {
         SendResult::Retry => {}
@@ -455,10 +501,15 @@ pub(crate) async fn send_msg_to_smtp(
                     .await?;
                 };
             }
-            context
-                .sql
-                .execute("DELETE FROM smtp WHERE id=?", (rowid,))
-                .await?;
+            if let Some(mut msg) = Message::load_from_db_optional(context, msg_id).await? {
+                message::set_msg_failed(context, &mut msg, &err.to_string()).await?;
+            }
+            if !unsent_saved {
+                context
+                    .sql
+                    .execute("DELETE FROM smtp WHERE id=?", (rowid,))
+                    .await?;
+            }
         }
     };
 
@@ -470,10 +521,39 @@ pub(crate) async fn send_msg_to_smtp(
             }
             Ok(())
         }
-        SendResult::Failure(err) => Err(format_err!("{err}")),
+        SendResult::Failure(err) => {
+            if unsent_saved {
+                Err(format_err!("Retry"))
+            } else {
+                Err(format_err!("{err}"))
+            }
+        }
     }
 }
 
+async fn max_smtp_rcpt_to(context: &Context, transport_id: u32) -> Result<usize> {
+    let limit = context
+        .sql
+        .query_row_optional(
+            "SELECT max_smtp_rcpt_to FROM transports WHERE id=?",
+            (transport_id,),
+            |row| row.get::<_, u32>(0),
+        )
+        .await?
+        .unwrap_or(0);
+
+    if limit > 0 {
+        return Ok(limit as usize);
+    }
+
+    let val = context
+        .get_configured_provider()
+        .await?
+        .and_then(|provider| provider.opt.max_smtp_rcpt_to)
+        .map_or(constants::DEFAULT_MAX_SMTP_RCPT_TO, usize::from);
+    Ok(val)
+}
+
 pub(crate) async fn msg_has_pending_smtp_job(
     context: &Context,
     msg_id: MsgId,
@@ -600,7 +680,7 @@ async fn send_mdn_rfc724_mid(
         })
         .collect();
 
-    match smtp_send(context, &recipients, &body, smtp, None).await {
+    match smtp_send(context, &recipients, &body, smtp).await {
         SendResult::Success => {
             if !recipients.is_empty() {
                 info!(context, "Successfully sent MDN for {rfc724_mid}.");
@@ -722,3 +802,22 @@ pub(crate) async fn add_self_recipients(
     }
     Ok(())
 }
+
+#[allow(clippy::arithmetic_side_effects)]
+pub(crate) async fn send_smtp_chunks(
+    context: &Context,
+    recipients: &[async_smtp::EmailAddress],
+    body: &str,
+    chunk_size: usize,
+    sender: &mut (dyn SmtpSender + Send),
+) -> (SendResult, usize) {
+    for (i, chunk) in recipients.chunks(chunk_size).enumerate() {
+        let status = sender.send_chunk(context, chunk, body).await;
+        match status {
+            SendResult::Success => continue,
+            SendResult::Failure(_) => return (status, (i + 1) * chunk_size),
+            SendResult::Retry => return (status, i * chunk_size),
+        }
+    }
+    (SendResult::Success, recipients.len())
+}

src/smtp/chunking_tests.rs

@@ -0,0 +1,102 @@
+use crate::smtp::{send_smtp_chunks, SendResult, SmtpSender};
+use crate::test_utils::TestContextManager;
+use crate::context::Context;
+use anyhow::Result;
+use futures::future::{BoxFuture, FutureExt};
+
+/// Result the mock should return on the designated call.
+enum MockFailure {
+    Transient,
+    Permanent,
+}
+
+struct MockSmtpSender {
+    call_count: usize,
+    fail_on_call: Option<(usize, MockFailure)>,
+}
+
+impl SmtpSender for MockSmtpSender {
+    fn send_chunk<'a>(
+        &'a mut self,
+        _context: &'a Context,
+        _recipients: &'a [async_smtp::EmailAddress],
+        _body: &'a str,
+    ) -> BoxFuture<'a, SendResult> {
+        self.call_count += 1;
+        let count = self.call_count;
+        let fail_on = self.fail_on_call.as_ref().map(|(n, _)| *n);
+        let is_permanent = matches!(
+            self.fail_on_call,
+            Some((_, MockFailure::Permanent))
+        );
+        async move {
+            if fail_on == Some(count) {
+                if is_permanent {
+                    return SendResult::Failure(
+                        anyhow::format_err!("permanent error"),
+                    );
+                }
+                return SendResult::Retry;
+            }
+            SendResult::Success
+        }
+        .boxed()
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_send_smtp_chunks() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = tcm.alice().await;
+
+    let recipients: Vec<_> = ["r1@ex.org", "r2@ex.org", "r3@ex.org", "r4@ex.org", "r5@ex.org"]
+        .iter()
+        .map(|a| async_smtp::EmailAddress::new(a.to_string()).unwrap())
+        .collect();
+
+    // All chunks succeed.
+    let mut sender = MockSmtpSender { call_count: 0, fail_on_call: None };
+    let (status, processed) =
+        send_smtp_chunks(&alice.ctx, &recipients, "body", 2, &mut sender).await;
+    assert!(matches!(status, SendResult::Success));
+    assert_eq!(processed, 5);
+    assert_eq!(sender.call_count, 3); // chunks: [2, 2, 1]
+
+    // Second chunk gets a transient error, only first chunk's recipients are processed.
+    let mut sender =
+        MockSmtpSender { call_count: 0, fail_on_call: Some((2, MockFailure::Transient)) };
+    let (status, processed) =
+        send_smtp_chunks(&alice.ctx, &recipients, "body", 2, &mut sender).await;
+    assert!(matches!(status, SendResult::Retry));
+    assert_eq!(processed, 2);
+    assert_eq!(sender.call_count, 2);
+
+    // Last chunk gets a transient error, first two chunks' recipients are processed.
+    let mut sender =
+        MockSmtpSender { call_count: 0, fail_on_call: Some((3, MockFailure::Transient)) };
+    let (status, processed) =
+        send_smtp_chunks(&alice.ctx, &recipients, "body", 2, &mut sender).await;
+    assert!(matches!(status, SendResult::Retry));
+    assert_eq!(processed, 4);
+    assert_eq!(sender.call_count, 3);
+
+    // Second chunk gets a permanent error; processed includes the failed chunk.
+    let mut sender =
+        MockSmtpSender { call_count: 0, fail_on_call: Some((2, MockFailure::Permanent)) };
+    let (status, processed) =
+        send_smtp_chunks(&alice.ctx, &recipients, "body", 2, &mut sender).await;
+    assert!(matches!(status, SendResult::Failure(_)));
+    assert_eq!(processed, 4);
+    assert_eq!(sender.call_count, 2);
+
+    // Last chunk gets a permanent error; processed includes the failed chunk.
+    let mut sender =
+        MockSmtpSender { call_count: 0, fail_on_call: Some((3, MockFailure::Permanent)) };
+    let (status, processed) =
+        send_smtp_chunks(&alice.ctx, &recipients, "body", 2, &mut sender).await;
+    assert!(matches!(status, SendResult::Failure(_)));
+    assert_eq!(processed, 6); // capped at (i+1)*chunk_size, may exceed len
+    assert_eq!(sender.call_count, 3);
+
+    Ok(())
+}

src/sql/migrations.rs

@@ -2385,6 +2385,15 @@ UPDATE msgs SET state=19 WHERE state=24; -- Change OutPreparing to OutFailed.
         .await?;
     }
 
+    inc_and_check(&mut migration_version, 153)?;
+    if dbversion < migration_version {
+        sql.execute_migration(
+            "ALTER TABLE transports ADD COLUMN max_smtp_rcpt_to INTEGER NOT NULL DEFAULT 0",
+            migration_version,
+        )
+        .await?;
+    }
+
     let new_version = sql
         .get_raw_config_int(VERSION_CFG)
         .await?

src/test_utils.rs

@@ -1685,7 +1685,7 @@ async fn write_msg(context: &Context, prefix: &str, msg: &Message, buf: &mut Str
         msg.get_id(),
         if msg.get_showpadlock() { "🔒" } else { "" },
         if msg.has_location() { "📍" } else { "" },
-        contact_name,
+        &contact_name,
         contact_id,
         msgtext,
         if msg.get_from_id() == ContactId::SELF {

src/tests/aeap.rs

@@ -161,7 +161,7 @@ async fn check_that_transition_worked(
             2,
             "Group {} has members {:?}, but should have members {:?} and {:?}",
             group,
-            members,
+            &members,
             alice_contact_id,
             ContactId::SELF
         );

src/tools.rs

@@ -62,13 +62,13 @@ pub(crate) fn truncate(buf: &str, approx_chars: usize) -> Cow<'_, str> {
     if let Some(index) = buf.get(..end_pos).and_then(|s| s.rfind([' ', '\n'])) {
         Cow::Owned(format!(
             "{}{}",
-            buf.get(..=index).unwrap_or_default(),
+            &buf.get(..=index).unwrap_or_default(),
             DC_ELLIPSIS
         ))
     } else {
         Cow::Owned(format!(
             "{}{}",
-            buf.get(..end_pos).unwrap_or_default(),
+            &buf.get(..end_pos).unwrap_or_default(),
             DC_ELLIPSIS
         ))
     }

src/tools/tools_tests.rs

@@ -247,12 +247,12 @@ proptest! {
         assert!(
             l <= approx_chars + el_len,
             "buf: '{}' - res: '{}' - len {}, approx {}",
-            buf, res, res.len(), approx_chars
+            &buf, &res, res.len(), approx_chars
         );
 
         if buf.chars().count() > approx_chars + el_len {
             let l = res.len();
-            assert_eq!(&res[l-5..l], "[...]", "missing ellipsis in {res}");
+            assert_eq!(&res[l-5..l], "[...]", "missing ellipsis in {}", &res);
         }
     }
 }

src/transport.rs

@@ -116,7 +116,7 @@ pub(crate) struct ConnectionCandidate {
 
 impl fmt::Display for ConnectionCandidate {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}:{}:{}", self.host, self.port, self.security)?;
+        write!(f, "{}:{}:{}", &self.host, self.port, self.security)?;
         Ok(())
     }
 }
@@ -131,7 +131,7 @@ pub(crate) struct ConfiguredServerLoginParam {
 
 impl fmt::Display for ConfiguredServerLoginParam {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}:{}", self.connection, self.user)?;
+        write!(f, "{}:{}", self.connection, &self.user)?;
         Ok(())
     }
 }