Typical log message:

Oct 7 11:39:36 hostname dovecot: imap(username): Fatal: master: service(imap): child 14864 killed with signal 11 (core dumped)

What triggers the problem:

User moving multiple messages to a subfolder via IMAP (from another account, on another server, client: Thunderbird). Moving single messages either does not trigger the problem, or with much lower probability (could not reproduce).

Version: $ dpkg -l 'dovecot*' Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Architecture Description +++-=====================================-=======================-=======================-================================================================================ un dovecot-common <none> <none> (no description available) ii dovecot-core 1:2.2.9-1ubuntu5 amd64 secure POP3/IMAP server - core files un dovecot-gssapi <none> <none> (no description available) ii dovecot-imapd 1:2.2.9-1ubuntu5 amd64 secure POP3/IMAP server - IMAP daemon un dovecot-ldap <none> <none> (no description available) un dovecot-lmtpd <none> <none> (no description available) un dovecot-managesieved <none> <none> (no description available) un dovecot-mysql <none> <none> (no description available) un dovecot-pgsql <none> <none> (no description available) un dovecot-pop3d <none> <none> (no description available) un dovecot-sieve <none> <none> (no description available) un dovecot-solr <none> <none> (no description available) un dovecot-sqlite <none> <none> (no description available) tamas@szob:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 15.04 Release: 15.04 Codename: vivid

Also tried 2.2.18 from Ubuntu wiley, same results.

Backtrace (I am not sure this is useful, extraced core from Ubuntu's Apport):

(gdb) bt full #0 0x00007f404e58e3b6 in mail_index_keywords_unref () from /usr/lib/dovecot/libdovecot-storage.so.0 No symbol table info available. #1 0x00007f404ea254ad in _start () No symbol table info available.

Any help would be appreciated, I am happy to provide more info if necessary.

Tamas