[Dovecot] dovecot lost mail! Cause?

[Lukas Haase]

Hi,

After using dovecot for several years now, today happend something which
makes me really feel unconfortable: An email received was just not
delivered properly, or, is lost! The mail (from an external server) was
sent to two local mailboxes, user1 and user2. user1 received the message
but for user2, it *magically* disappeared.

MTA is exim4 which definitely processed the messages and handed over to
dovecot deliver:

2012-11-12 07:28:21 1TXnVG-00053I-GD SA: [...] id=8644593.887351352701
685934.JavaMail
2012-11-12 07:28:21 1TXnVG-00053I-GD => user1 <user1 at example.com>
R=dovecot T=dovecot_pipe
2012-11-12 07:28:21 1TXnVG-00053I-GD => user2 <user2 at example.com>
R=dovecot T=dovecot_pipe
2012-11-12 07:28:21 1TXnVG-00053I-GD Completed

Also, the log of dovecot tells that the mail should have been stored:

Nov 12 07:28:21 mail dovecot: deliver(user1): sieve:
msgid=<8644593.887351352701685934.JavaMail>: stored mail into mailbox
'INBOX'
Nov 12 07:28:21 mail dovecot: deliver(user2): sieve:
msgid=<8644593.887351352701685934.JavaMail.orbitz>: stored mail into
mailbox 'INBOX'

user1 received the mail but user2 not. Since user2 is myself, I *know*
that I did not accidently delete any mail or something like that. It was
just never received!

Disk space is 3GB left, so enough.

So I grepped the whole Maildir of user2 for the message ID. There is
only one match in the dovecot.index.cache and within that, the most
important data of the mail (Message ID, Date, Sender, Receiver, Subject)
appears. But apart from that, not a single file!

Is there hope to ever find out why what was going wrong here? It feels
me veeeeeeeeery unconfortable because from now on I can never be sure
any more that all my mails are really received :( :( However, as I said,
my mail system processed maybe millions of messages the past 8 years.
Although, I can not be sure if that was the case ... :(

And help greatly appreciated!

Luke

PS: Dovecot version 1.2.15 (Debian 6.0.6) with Maildir backend on local
harddrive. No NFS, nothing which can go wrong ...

PPS: Original log files, just named replaced for privacy.