Configure error with "Winmail Pro Mail Server" which does not provide UIDNEXT for Inbox

[NickLiu635]

• Operating System (Linux/Mac/Windows/iOS/Android): Windows
• Delta Chat Version:1.38.1 g5ff6e1e3
• Expected behavior:
  login success
• Actual behavior:
  login failed, but "Deltachat"mailbox was created in server
• Steps to reproduce the problem:
  login with email & pwd in an offline environment
• Screenshots:
• Logs:
  info imap.rs:1732 FINASHED configuring IMAP-folders
  warning imap.rs:647 IMAP folder has no uid_next, fall back to fetching
  error LoginForm.tsx:415:15 condigure error {"code":-1, "message":"could not read INBOX status Caused by: select: failed to fetch"}

[gerryfrancis]

login with email & pwd in an offline environment

@NickLiu635 Not sure if I understand, but how can anyone log in when the device is offline?

[link2xt]

This log means that INBOX mailbox did not return UIDNEXT when selected. According to RFC 3501 this is required, but older servers not supporting IMAP4rev1 may not send it.

@NickLiu635 Could you provide more details on which server it is, e.g. is it a Dovecot server or something else? Is the account on the server new? Does the INBOX contain any message? More logs could be helpful, Delta Chat should report IMAP server name on top.

[NickLiu635]

offline?

I want to use Deltachat in an intrante environment without Internet connection.

[NickLiu635]

This log means that INBOX mailbox did not return UIDNEXT when selected. According to RFC 3501 this is required, but older servers not supporting IMAP4rev1 may not send it.

@NickLiu635 Could you provide more details on which server it is, e.g. is it a Dovecot server or something else? Is the account on the server new? Does the INBOX contain any message? More logs could be helpful, Delta Chat should report IMAP server name on top.

It seems like the server is an old version of winmail (https://www.winmail.cn/) . The provider provides a test server with latest version at https://demo.winmail.cn:6443/ with username test and password wm001 . but the test server may not provide IMAP service...

I tried Deltachat version 1.40.4, but failed to login again with same log...
MVBOX-folder "DeltaChat" had been created successful...

[NickLiu635]

seems like issue happened here:

        let new_uid_next = match mailbox.uid_next {
            Some(uid_next) => uid_next,
            None => {      // <----- here
                warn!(
                    context,
                    "IMAP folder {folder:?} has no uid_next, fall back to fetching."
                );
                // note that we use fetch by sequence number
                // and thus we only need to get exactly the
                // last-index message.
                let set = format!("{}", mailbox.exists);
                let mut list = session
                    .inner
                    .fetch(set, JUST_UID)
                    .await
                    .context("Error fetching UID")?;

                let mut new_last_seen_uid = None;
                while let Some(fetch) = list.try_next().await? {
                    if fetch.message == mailbox.exists && fetch.uid.is_some() {
                        new_last_seen_uid = fetch.uid;
                    }
                }
                new_last_seen_uid.context("select: failed to fetch")? + 1        // <----- then here
            }
        };

[link2xt]

Are you running the server yourself? If you can provide credentials for a testing account that would be helpful. I may also be possible to follow https://www.winmail.cn/winmailpro_install.php and install https://dl.winmail.cn/download/winmail-pro-5.1-0616-x86_64.tar.gz on a Linux VM for testing, despite the name it seems the server supports Linux.

winmail.cn seems to be running thir server on port 993:

* OK Winmail Server Secure IMAP4 Ready
? ID foobar
* ID ("name" "Winmail Pro Mail Server" "version" "5.1.0616")
? OK ID completed

But I cannot login with demo account there.

[link2xt]

I have installed the server, there is indeed no UIDNEXT:

* OK example. Winmail Pro Mail Server IMAP4 ready
? LOGIN deltachat@example.org oaF0quax
? OK LOGIN Ok
? SELECT INBOX
* FLAGS (\Draft \Answered \Flagged \Deleted \Seen \Recent)
* OK [PERMANENTFLAGS (\Draft \Answered \Flagged \Deleted \Seen)] Limited
* 1 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1697802109] Ok
? OK [READ-WRITE] Ok SELECT completed

This is a Dovecot server for comparison:

* OK [CAPABILITY IMAP4rev1 IDLE MOVE QUOTA CONDSTORE AUTH=PLAIN] Dovecot (Debian) ready.
? LOGIN login@example.org password
? OK [CAPABILITY IMAP4rev1 IDLE MOVE QUOTA CONDSTORE] Logged in
? SELECT INBOX
* FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
* OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)] Flags permitted.
* 0 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1697802745] UIDs valid
* OK [UIDNEXT 1] Predicted next UID
? OK [READ-WRITE] Select completed (0.006 + 0.000 + 0.005 secs).

However, I also configured Delta Chat from repl against Winmail server I have setup, and for me it works, here is the log:

 INFO  deltachat_repl > src/imap.rs:1749: Using "/" as folder-delimiter.
 INFO  deltachat_repl > src/imap.rs:1681: Looking for MVBOX-folder "DeltaChat"...
 INFO  deltachat_repl > src/imap.rs:1684: MVBOX-folder "DeltaChat" successfully selected, using it.
 INFO  deltachat_repl > src/imap.rs:1761: Setting MVBOX FOLDER TO DeltaChat
 INFO  deltachat_repl > src/imap.rs:1774: FINISHED configuring IMAP-folders.
 WARN  deltachat_repl > src/imap.rs:647: IMAP folder "INBOX" has no uid_next, fall back to fetching.
 INFO  deltachat_repl > src/imap.rs:686: uid/validity change folder INBOX: new 2/1697802109 previous 0/0.
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(910 ‰)
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(920 ‰)
 INFO  deltachat_repl > src/key.rs:214: Generating keypair with type Default
 INFO  deltachat_repl > src/key.rs:220: Keypair generated in 0s.
 INFO  deltachat_repl > src/configure.rs:481: key generation completed
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(940 ‰)
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(1000 ‰)

I also tried removing the mail that exists in the mailbox by default, nothing surprising as well, configure succeeded:

 INFO  deltachat_repl > src/imap.rs:1749: Using "/" as folder-delimiter.
 INFO  deltachat_repl > src/imap.rs:1681: Looking for MVBOX-folder "DeltaChat"...
 INFO  deltachat_repl > src/imap.rs:1684: MVBOX-folder "DeltaChat" successfully selected, using it.
 INFO  deltachat_repl > src/imap.rs:1761: Setting MVBOX FOLDER TO DeltaChat
 INFO  deltachat_repl > src/imap.rs:1774: FINISHED configuring IMAP-folders.
 INFO  deltachat_repl > src/imap.rs:631: Folder "INBOX" is empty.
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(910 ‰)
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(920 ‰)
 INFO  deltachat_repl > src/key.rs:214: Generating keypair with type Default
 INFO  deltachat_repl > src/key.rs:220: Keypair generated in 0s.
 INFO  deltachat_repl > src/configure.rs:481: key generation completed
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(940 ‰)
 INFO  deltachat_repl > Received CONFIGURE_PROGRESS(1000 ‰)

There is a special code path for the case of empty folder:
https://github.com/deltachat/deltachat-core-rust/blob/16320357845da5cd963f7f3597c2ae18a2b8b6b9/src/imap.rs#L630-L640

[link2xt]

Ah, I see the problem. EXISTS is just the count of messages, e.g. it is 1 if there is one message. We should fetch * rather than EXISTS value, because there may be only one message with UID 15 or any other number, in this case EXISTS 1 will be returned, but we need to fetch UID 15 and store its UID.

EDIT: no, actually what we do is correct and works like this:

? FETCH 1 UID
* 1 FETCH (UID 2)
? OK FETCH completed

[link2xt]

So the problem is:

1. The server does not report UIDNEXT, confirmed.
2. It returns non-zero EXISTS, say EXISTS 20 meaning there are 20 messages in the INBOX.
3. When requested with FETCH 20 UID command, it returns no result. This one I can't reproduce with Winmail 5.1.

[link2xt]

I however discovered that STATUS command works against Winmail:

? STATUS INBOX (UIDNEXT)
* STATUS "INBOX" (UIDNEXT 4)
? OK STATUS completed

Probably this is what we should use in any case and drop the FETCH approach which does not look too reliable anyway as there is no guarantee that the message with the highest sequence has the highest UID. I would like Delta Chat core to never use sequence numbers at all, even for this fallback FETCH command.