feat: Don't mark messages as seen on IMAP if bcc_self=0 or bot=1

bcc_self=0 means that the user disabled it or it's a chatmail setup with the only device and w/o
backups. If a backup is made someday, old messages not marked as IMAP-seen aren't a problem and new
ones are marked as IMAP-seen.

For bots, particularly multi-device ones (which are a rare case), probably no sane logic can be
built on the "seen" message status. Moreover, if the user has additionally a bot that reads incoming
messages, it doesn't mean that the user doesn't want to read them too.

Also don't mark a message as IMAP-seen just if it already exists on the device as this doesn't mean
that it exists on another device.

Also don't mark MDNs and DSNs as IMAP-seen. Marking MDNs as seen is useless, they shouldn't be
displayed by any MUA. Auto-marking DSNs as seen should be avoided because the user may want to see
them in another MUA.

Author: iequidoo

deltachat-rpc-client/tests/test_multidevice.py

@@ -44,7 +44,6 @@ def test_one_account_send_bcc_setting(acfactory, log, direct_imap):
 
     # now make sure we are sending message to ourselves too
     assert self_addr in ev.msg
-    assert self_addr in ev.msg
 
     # BCC-self messages are marked as seen by the sender device.
     while True:

src/imap.rs

@@ -2248,11 +2248,16 @@ pub(crate) async fn prefetch_should_download(
     message_id: &str,
     mut flags: impl Iterator<Item = Flag<'_>>,
 ) -> Result<bool> {
-    if message::rfc724_mid_exists(context, message_id)
-        .await?
-        .is_some()
+    if let Some((.., seen)) = message::rfc724_mid_exists_ex(
+        context,
+        message_id,
+        "state>=16", // `InSeen`
+    )
+    .await?
     {
-        markseen_on_imap_table(context, message_id).await?;
+        if seen {
+            markseen_on_imap_table(context, message_id).await?;
+        }
         return Ok(false);
     }
 
@@ -2397,6 +2402,11 @@ async fn mark_seen_by_uid(
 /// Schedule marking the message as Seen on IMAP by adding all known IMAP messages corresponding to
 /// the given Message-ID to `imap_markseen` table.
 pub(crate) async fn markseen_on_imap_table(context: &Context, message_id: &str) -> Result<()> {
+    if !context.get_config_bool(Config::BccSelf).await?
+        || context.get_config_bool(Config::Bot).await?
+    {
+        return Ok(());
+    }
     context
         .sql
         .execute(

src/receive_imf.rs

@@ -993,11 +993,6 @@ pub(crate) async fn receive_imf_inner(
                 )
                 .await?;
         }
-        if target.is_none() && !mime_parser.mdn_reports.is_empty() && mime_parser.has_chat_version()
-        {
-            // This is a Delta Chat MDN. Mark as read.
-            markseen_on_imap_table(context, rfc724_mid_orig).await?;
-        }
     }
 
     if mime_parser.is_call() {
@@ -1145,8 +1140,9 @@ async fn decide_chat_assignment(
         info!(context, "Message is an MDN (TRASH).");
         true
     } else if mime_parser.delivery_report.is_some() {
+        // Auto-marking DSNs as IMAP-seen should be avoided because the user may want to see them in
+        // another MUA.
         info!(context, "Message is a DSN (TRASH).");
-        markseen_on_imap_table(context, rfc724_mid).await.ok();
         true
     } else if mime_parser.get_header(HeaderDef::ChatEdit).is_some()
         || mime_parser.get_header(HeaderDef::ChatDelete).is_some()