dovecot - May 2014 - Corrupted mailbox, how to fix?

>From my log:
May 06 16:26:49 imap(loginname): Error:
zlib.read(/var/mail/loginname/mdbox/storage/m.94): gz trailer has wrong CRC
value at 2412347
May 06 16:26:49 imap(loginname): Error: read() failed: Invalid argument (FETCH
for mailbox INBOX UID 3434)

How do I fix that?

-- 
Ralf Hildebrandt
  Gesch?ftsbereich IT | Abteilung Netzwerk
  Charit? - Universit?tsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  ralf.hildebrandt at charite.de | http://www.charite.de

On Wed, 2014-05-07 at 15:36 +0200, Ralf Hildebrandt
wrote:
> From my log:
> 
> May 06 16:26:49 imap(loginname): Error:
zlib.read(/var/mail/loginname/mdbox/storage/m.94): gz trailer has wrong CRC
value at 2412347
> May 06 16:26:49 imap(loginname): Error: read() failed: Invalid argument
(FETCH for mailbox INBOX UID 3434)
> 
> How do I fix that?
With some difficulties. I'm not sure how Dovecot could even handle
corrupted compression in any good way. Currently it treats it the same
way as temporary disk I/O error, which I guess isn't that great if there
really is corruption that doesn't fix itself.

Anyway, for now you'd basically need to get rid of the broken mail in
some way. First find out which mail it is, then try to make a copy of it
that hopefully is mostly correct (e.g. doveadm fetch > file), upload the
working copy back (dovecot-lda) and delete the original broken one.