Dsync deleting mailboxes due to duplicate UIDs

[Andreas Thienemann]

Hi Sami,

On Sun, 9 Sep 2018, Sami Ketola wrote:

>  Is it possible to get imapc rawlogs to analyze? create a directory that is
>  writeable and add -o imapc_rawlog_dir=/path/to/directory to command line.

Tried that. Thanks for the suggestion, that is actually really helpful.
If anyone wants to play along at home, the files in that directory are created 
with the permissions of mail_uid/mail_gid. The dir should be world-writable to 
make it easy.

>  Also with recent dovecot release you can tell dsync which header fields to
>  hash when matching mails. Add dsync_hashed_headers=Message-ID to config and
>  dovecot will only mach mails using Message-ID header fileld.

I had seen that parameter but thought it would be prudent to not _just_ rely on 
the Message-ID but instead keep the default "Date Message-ID".

I _think_ I might have found an issue when looking at the log:

1536525811.026071 * 39 FETCH (UID 39 BODY[HEADER.FIELDS (Date Message-ID)] {159}
1536525811.026071 Message-ID: <Pine.LNX.4.30.0207091925420.433-100000 at trinity.knopfdruck.org>
1536525811.026071 Date: Tue, 9 Jul 2002 19:26:04 +0200 (MEST)
1536525811.026071 Date: Tue, 9 Jul 2002 12:36:13 +0200
1536525811.026071
1536525811.026071 )

A duplicate Date header is certainly unexpected. Having a look at the original 
mail on disk on the Cyrus server shows the following Mail:

>From [redacted] Tue Jul  9 19:26:04 2002
X-Sieve: cmu-sieve 1.3
Return-Path: [redacted]
Received: from bender.bawue.de (localhost [127.0.0.1])
          by bender.bawue.de (Postfix) with ESMTP
          id C79CE48CBC; Tue,  9 Jul 2002 19:29:08 +0200 (CEST)
Delivered-To: [redacted]
Received: from [redacted]
          by bender.bawue.de (Postfix) with ESMTP id CFA4848CAA
          for [redacted]; Tue,  9 Jul 2002 19:28:43 +0200 (CEST)
From: [redacted]
X-Sender:  [redacted]
To: [redacted]
Message-ID: <Pine.LNX.4.30.0207091925420.433-100000 at trinity.knopfdruck.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN;
   charset=ISO-8859-1
Content-Transfer-Encoding: 8BIT
Subject: [redacted]
Date: Tue, 9 Jul 2002 19:26:04 +0200 (MEST)
Status: RO
X-Status:
X-Keywords:
X-UID: 38

---------- Forwarded message ----------
Date: Tue, 9 Jul 2002 12:36:13 +0200
Subject: Gewinn

[redacted]


So it looks like the Cyrus imapd is incorrectly parsing the mail and returning 
the body content as a header. Comparing the content of UID 39 on the remote 
server will then hash differently than the UID 39 on the local dovecot server, 
which behaves better and only returns a single date header.

Following the robustness principle it feels to me that it would make sense for 
dsync to disregard a duplicate header from a remote server and only use the 
first occurence.

Would that be a good approach to the problem? Now that I understand the problem 
I am having, I can just workaround it but it seems to me that dsync should 
handle this case better.

Anyway, thanks a lot for the imapc_rawlog_dir hint, that helped a lot.

cheers,
   Andreas