dovecot version: 2.2.13 NetBSD 5.1 on an amd64 architecture
Based on the log file, I think this problem first manifested itself when I upgrade from 2.2.9 to 2.2.12. I tried to go back to 2.2.9, but I would have had to rollback some of the other dependencies. I built 2.2.13 and the problem still exists.
Mail gets successfully delivered, but the sender get a non-delivery message. I've hacked a temporary workaround to prevent the non-delivery from being sent by having the bounce service run discard instead of bounce.
Logfile excerpt:
May 18 04:37:07 chaos postfix/smtp[27935]: 39F8B2134F: to=XXXX@YYYY.ZZZ, relay=127.0.0.1[127.0.0.1]:10024, delay=21, delays=1.9/0.13/0.69/18, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as 0538621350)
May 18 04:37:07 chaos postfix/qmgr[19537]: 39F8B2134F: removed
May 18 04:37:07 chaos dovecot: lda(XXXX@YYYY.ZZZ): msgid=MAILSM200e8021240fd744d9d8094cd0c3e82dfc2@MAILSM200: saved mail to INBOX
May 18 04:37:07 chaos postfix/pipe[12775]: 0538621350: to=XXXX@YYYY.ZZZ, relay=dovecot, delay=0.54, delays=0.07/0.3/0/0.18, dsn=5.3.0, status=bounced (Command died with signal 11: "/usr/pkg/libexec/dovecot/dovecot-lda")
May 18 04:37:07 chaos postfix/cleanup[2233]: 88C0221353: message-id=20140518043707.88C0221353@chaos.dishaw.org
May 18 04:37:07 chaos postfix/bounce[18857]: 0538621350: sender non-delivery notification: 88C0221353
May 18 04:37:07 chaos postfix/qmgr[19537]: 88C0221353: from=<>, size=14448, nrcpt=1 (queue active)
May 18 04:37:07 chaos postfix/qmgr[19537]: 0538621350: removed
May 18 04:37:08 chaos postfix/smtp[20299]: 88C0221353: to=AAAA@BBBB.CCC,relay=site.careerbuilder.com[208.82.4.130]:25, delay=0.89, delays=0.03/0.03/0.25/0.58, dsn=2.6.0, status=sent (250 2.6.0 message received)
May 18 04:37:08 chaos postfix/qmgr[19537]: 88C0221353: removed
Backtrace: #0 0x00007f7ffc907270 in ?? () #1 0x00007f7ffd778498 in lib_signals_deinit () from /usr/pkg/lib/dovecot/libdovecot.so.0 #2 0x00007f7ffd725739 in master_service_deinit () from /usr/pkg/lib/dovecot/libdovecot.so.0 #3 0x0000000000403021 in main ()