feat: Add system message when provider does not allow unencrypted messages (#5161) (#5195)

close #5161

![Screenshot from 2024-01-19
19-56-09](https://github.com/deltachat/deltachat-core-rust/assets/39526136/27ecdd9b-1739-410b-bb26-80d5bdbbc39a)

---------

Co-authored-by: bjoern <r10s@b44t.com>

deltachat-jsonrpc/src/api/types/message.rs

@@ -345,6 +345,7 @@ pub enum SystemMessageType {
     SecurejoinMessage,
     LocationStreamingEnabled,
     LocationOnly,
+    InvalidUnencryptedMail,
 
     /// Chat ephemeral message timer is changed.
     EphemeralTimerChanged,
@@ -385,6 +386,7 @@ impl From<deltachat::mimeparser::SystemMessage> for SystemMessageType {
             SystemMessage::MultiDeviceSync => SystemMessageType::MultiDeviceSync,
             SystemMessage::WebxdcStatusUpdate => SystemMessageType::WebxdcStatusUpdate,
             SystemMessage::WebxdcInfoMessage => SystemMessageType::WebxdcInfoMessage,
+            SystemMessage::InvalidUnencryptedMail => SystemMessageType::InvalidUnencryptedMail,
         }
     }
 }

src/mimeparser.rs

@@ -176,6 +176,10 @@ pub enum SystemMessage {
     /// "%1$s sent a message from another device."
     ChatProtectionDisabled = 12,
 
+    /// Message can't be sent because of `Invalid unencrypted mail to <>`
+    /// which is sent by chatmail servers.
+    InvalidUnencryptedMail = 13,
+
     /// Self-sent-message that contains only json used for multi-device-sync;
     /// if possible, we attach that to other messages as for locations.
     MultiDeviceSync = 20,

src/smtp.rs

@@ -10,6 +10,7 @@ use async_smtp::{self as smtp, EmailAddress, SmtpTransport};
 use tokio::io::BufStream;
 use tokio::task;
 
+use crate::chat::{add_info_msg_with_cmd, ChatId};
 use crate::config::Config;
 use crate::contact::{Contact, ContactId};
 use crate::context::Context;
@@ -26,6 +27,7 @@ use crate::provider::Socket;
 use crate::scheduler::connectivity::ConnectivityStore;
 use crate::socks::Socks5Config;
 use crate::sql;
+use crate::stock_str::unencrypted_email;
 
 /// SMTP connection, write and read timeout.
 const SMTP_TIMEOUT: Duration = Duration::from_secs(60);
@@ -584,7 +586,46 @@ pub(crate) async fn send_msg_to_smtp(
 
     match status {
         SendResult::Retry => {}
-        SendResult::Success | SendResult::Failure(_) => {
+        SendResult::Success => {
+            context
+                .sql
+                .execute("DELETE FROM smtp WHERE id=?", (rowid,))
+                .await?;
+        }
+        SendResult::Failure(ref err) => {
+            if err.to_string().contains("Invalid unencrypted mail") {
+                let res = context
+                    .sql
+                    .query_row_optional(
+                        "SELECT chat_id, timestamp FROM msgs WHERE id=?;",
+                        (msg_id,),
+                        |row| Ok((row.get::<_, ChatId>(0)?, row.get::<_, i64>(1)?)),
+                    )
+                    .await?;
+
+                if let Some((chat_id, timestamp_sort)) = res {
+                    let addr = context.get_config(Config::ConfiguredAddr).await?;
+                    let text = unencrypted_email(
+                        context,
+                        addr.unwrap_or_default()
+                            .split('@')
+                            .nth(1)
+                            .unwrap_or_default(),
+                    )
+                    .await;
+                    add_info_msg_with_cmd(
+                        context,
+                        chat_id,
+                        &text,
+                        crate::mimeparser::SystemMessage::InvalidUnencryptedMail,
+                        timestamp_sort,
+                        None,
+                        None,
+                        None,
+                    )
+                    .await?;
+                };
+            }
             context
                 .sql
                 .execute("DELETE FROM smtp WHERE id=?", (rowid,))

src/stock_str.rs

@@ -419,6 +419,11 @@ pub enum StockMessage {
 
     #[strum(props(fallback = "Member %1$s added."))]
     MsgAddMember = 173,
+
+    #[strum(props(
+        fallback = "⚠️ Your email provider %1$s requires end-to-end encryption which is not setup yet."
+    ))]
+    InvalidUnencryptedMail = 174,
 }
 
 impl StockMessage {
@@ -1285,6 +1290,13 @@ pub(crate) async fn aeap_addr_changed(
         .replace3(new_addr)
 }
 
+/// Stock string: `⚠️ Your email provider %1$s requires end-to-end encryption which is not setup yet. Tap to learn more.`.
+pub(crate) async fn unencrypted_email(context: &Context, provider: &str) -> String {
+    translated(context, StockMessage::InvalidUnencryptedMail)
+        .await
+        .replace1(provider)
+}
+
 pub(crate) async fn aeap_explanation_and_link(
     context: &Context,
     old_addr: &str,