Pigeonhole 0.4.10 doesn't log msgid for some messages.
Dec 16 09:57:57 mx dovecot: lmtp(us...@example.com): EbLlL2gLcVYCBgEAPZa6/Q: sieve: msgid=<20151216065756.be1df1f...@cp.bitrix24.com>: forwarded to <us...@example.com> Dec 16 09:57:57 mx dovecot: lmtp(us...@example.com): EbLlL2gLcVYCBgEAPZa6/Q: sieve: stored mail into mailbox 'INBOX' Dec 16 09:57:57 mx dovecot: lmtp(us...@example.com): FrLlL2gLcVYCBgEAPZa6/Q: sieve: msgid=<20151216065756.c77bb1f...@cp.bitrix24.com>: forwarded to <us...@example.com> Dec 16 09:57:57 mx dovecot: lmtp(us...@example.com): FrLlL2gLcVYCBgEAPZa6/Q: sieve: msgid=<20151216065756.c77bb1f...@cp.bitrix24.com>: stored mail into mailbox 'bitrix'