Hi all,

I’m using mailcow for several years now and have a fantastic experience.

Recently my users have reported that they are missing some mails form a specific users on a specific domain.

When looking through postfix logs I have noticed a lot of 4.7.1 Service unavailable but with very little more details.

postfix-mailcow-1 | Nov 15 14:44:42 1c5b738c0235 postfix/cleanup[156298]: 79FE52009FE: milter-reject: END-OF-MESSAGE from s6c.cyber-folks.pl[185.208.164.6]: 4.7.1 Service unavailable - try again later; from=<mail@domain.info> to=<j.k@mm.pl> proto=ESMTP helo=<s6c.cyber-folks.pl> postfix-mailcow-1 | Nov 15 22:57:06 1c5b738c0235 postfix/cleanup[159715]: 996B82006BD: milter-reject: END-OF-MESSAGE from s6c.cyber-folks.pl[185.208.164.6]: 4.7.1 Service unavailable - try again later; from=<mail@domain.info> to=<j.k@mm.pl> proto=ESMTP helo=<s6c.cyber-folks.pl> postfix-mailcow-1 | Nov 16 07:12:09 1c5b738c0235 postfix/cleanup[162495]: 20C8E2006BD: milter-reject: END-OF-MESSAGE from s6c.cyber-folks.pl[185.208.164.6]: 4.7.1 Service unavailable - try again later; from=<mail@domain.info> to=<j.k@mm.pl> proto=ESMTP helo=<s6c.cyber-folks.pl> postfix-mailcow-1 | Nov 16 13:25:03 1c5b738c0235 postfix/cleanup[164567]: EE25B200A6C: milter-reject: END-OF-MESSAGE from s6c.cyber-folks.pl[185.208.164.6]: 4.7.1 Service unavailable - try again later; from=<mail@domain.info> to=<j.k@mm.pl> proto=ESMTP helo=<s6c.cyber-folks.pl> postfix-mailcow-1 | Nov 19 08:37:48 1c5b738c0235 postfix/cleanup[194201]: F05AC2024E7: replace: header Received: from 8d74eaa4408d (mailcowdockerized-sogo-mailcow-1.mailcowdockerized_mailcow-network [172.22.1.248])??(Authenticated sender: k.n@mm.com)??by mail.mm.com (Postcow) with ESM from mailcowdockerized-sogo-mailcow-1.mailcowdockerized_mailcow-network[172.22.1.248]; from=<k.n@mm.pl> to=<mail@domain.info> proto=ESMTP helo=<8d74eaa4408d>: Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPA id F05AC2024E7;??Wed, 19 Nov 2025 08:37:48 +0100 (CET) postfix-mailcow-1 | Nov 19 08:37:53 1c5b738c0235 postfix/smtp[194204]: F05AC2024E7: to=<mail@domain.info>, relay=mail.domain.info[185.208.164.106]:25, delay=5, delays=0.75/0.05/0.22/4, dsn=2.0.0, status=sent (250 OK id=1vLclC-0000000EKo2-2yql) postfix-mailcow-1 | Nov 20 09:27:23 1c5b738c0235 postfix/cleanup[205123]: 8C24E2025CB: replace: header Received: from 8d74eaa4408d (mailcowdockerized-sogo-mailcow-1.mailcowdockerized_mailcow-network [172.22.1.248])??(Authenticated sender: k.n@mm.com)??by mail.mm.com (Postcow) with ESM from mailcowdockerized-sogo-mailcow-1.mailcowdockerized_mailcow-network[172.22.1.248]; from=<k.n@mm.pl> to=<mail@domain.info> proto=ESMTP helo=<8d74eaa4408d>: Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPA id 8C24E2025CB;??Thu, 20 Nov 2025 09:27:23 +0100 (CET) postfix-mailcow-1 | Nov 20 09:27:25 1c5b738c0235 postfix/smtp[205124]: 8C24E2025CB: to=<mail@domain.info>, relay=mail.domain.info[185.208.164.106]:25, delay=2.2, delays=0.57/0.05/0.19/1.4, dsn=2.0.0, status=sent (250 OK id=1vM00i-000000066hA-2dlb) postfix-mailcow-1 | Nov 20 14:03:06 1c5b738c0235 postfix/smtp[208002]: 7DB10202554: to=<mail@domain.info>, relay=mail.domain.info[185.208.164.106]:25, delay=20, delays=2.1/0.01/0.3/17, dsn=2.0.0, status=sent (250 OK id=1vM4JG-0000000DwwE-1ExJ)

Details on a example failed mail
postfix-mailcow-1 | Nov 16 13:24:59 1c5b738c0235 postfix/smtpd[164566]: EE25B200A6C: client=s6c.cyber-folks.pl[185.208.164.6] postfix-mailcow-1 | Nov 16 13:25:00 1c5b738c0235 postfix/cleanup[164567]: EE25B200A6C: message-id=<809e0ebed6dd5aef8d7b8cc134f993ed@domain.info> postfix-mailcow-1 | Nov 16 13:25:03 1c5b738c0235 postfix/cleanup[164567]: EE25B200A6C: milter-reject: END-OF-MESSAGE from s6c.cyber-folks.pl[185.208.164.6]: 4.7.1 Service unavailable - try again later; from=<j.o@domain.info> to=<j.k@mm.pl> proto=ESMTP helo=<s6c.cyber-folks.pl>

Details of na example working email
docker compose logs postfix-mailcow | grep "5790B201543" postfix-mailcow-1 | Nov 20 15:02:29 1c5b738c0235 postfix/smtpd[208563]: 5790B201543: client=s6c.cyber-folks.pl[185.208.164.6] postfix-mailcow-1 | Nov 20 15:02:29 1c5b738c0235 postfix/cleanup[208564]: 5790B201543: message-id=<2cd2a4d95d51a71baf99d93fe7f6970a@zb.info> postfix-mailcow-1 | Nov 20 15:02:29 1c5b738c0235 postfix/qmgr[378]: 5790B201543: from=<d.c@zb.info>, size=3176, nrcpt=2 (queue active) postfix-mailcow-1 | Nov 20 15:02:30 1c5b738c0235 postfix/lmtp[208531]: 5790B201543: to=<k.n@mm.com>, orig_to=<k.n@mm.com>, relay=dovecot[172.22.1.250]:24, delay=0.67, delays=0.65/0.01/0/0.01, dsn=2.0.0, status=sent (250 2.0.0 <k.n@mm.com> 0AF+AHYfH2k5oi8AIO5+eg Saved) postfix-mailcow-1 | Nov 20 15:02:30 1c5b738c0235 postfix/lmtp[208532]: 5790B201543: to=<a.k@mm.com>, orig_to=<a.k@mm.com>, relay=dovecot[172.22.1.250]:24, delay=0.68, delays=0.65/0.01/0.01/0.02, dsn=2.0.0, status=sent (250 2.0.0 <a.k@mm.com> aPqIAHYfH2nLny8AIO5+eg Saved) postfix-mailcow-1 | Nov 20 15:02:30 1c5b738c0235 postfix/qmgr[378]: 5790B201543: removed

The sender domain is whitelisted, and if a mail works fine it is reported by Rspamd
When it fails no indication of an email in Rspamd can be found

I’m struggling to find any reasons on why

The sender domain has 2 users (j.o and d.c) and mails from one are delivered with no problems, and the second will have an error in same point in time.

How to get more details for such error or where to look next