Sudden breakage of my dovecot services?

Simile8008

Hi, I’ve been using Mailcow-Dockerized for about 2 years (mostly) without issues. However within the last few days it appears some way or another that I can no longer receive emails. Sending works great and mail-tester.com gives me a 10/10. The DNS domain tests built within Mailcow all return successful. I have not edited my DNS settings regarding mail in roughly a year according to deSEC’s admin interface, and like I said this is an extremely recent problem, I have had no problems receiving mail up until this point. I run my server at home on a residential IP address with SMTP fowarding with another provider. When I try sending emails to myself from another email provider, this is the error I get back:

<testing.email@mydomain.tld>: Host or domain name not found. Name service
    error for name=mail.mydomain.tld type=A: Host found but no data record of
    requested type

----------------------------------------------
message/delivery-status
----------------------------------------------
Reporting-MTA: dns; mail-244102.otherservice.com
X-Postfix-Queue-ID: XXXXXXXXXXXX
X-Postfix-Sender: rfc822; my-alt-email@otherservice.com
Arrival-Date: Fri, 18 Jul 2025 18:26:05 +0000 (UTC)

Final-Recipient: rfc822; testing.email@mydomain.tld
Original-Recipient: rfc822;testing.email@mydomain.tld
Action: failed
Status: 5.4.4
Diagnostic-Code: X-Postfix; Host or domain name not found. Name service error
    for name=mail.mydomain.tld type=A: Host found but no data record of
    requested type

I have DDNS set up for mail.mydomain.tld (in addition to a wildcard record) and the A & AAAA records are current. I double checked them with nslookup. I am not sure what I need to do from here, as postfix logs don’t look to be very helpful either.

 docker compose logs -f postfix-mailcow
opostfix-mailcow-1  | 2025-07-18 10:14:29,156 INFO Set uid to user 0 succeeded
postfix-mailcow-1  | 2025-07-18 10:14:29,157 INFO supervisord started with pid 1
postfix-mailcow-1  | 2025-07-18 10:14:30,141 INFO spawned: 'processes' with pid 8
postfix-mailcow-1  | 2025-07-18 10:14:30,145 INFO spawned: 'postfix' with pid 9
postfix-mailcow-1  | 2025-07-18 10:14:30,146 INFO spawned: 'syslog-ng' with pid 10
postfix-mailcow-1  | Uptime: 31  Threads: 7  Questions: 365  Slow queries: 0  Opens: 60  Open tables: 53  Queries per second avg: 11.774
postfix-mailcow-1  | Jul 18 10:14:30 1be0597f9620 syslog-ng[10]: syslog-ng starting up; version='3.38.1'
postfix-mailcow-1  | Checking if ASN for your IP is listed for Spamhaus Bad ASN List...
postfix-mailcow-1  | The AS of your IP is NOT listed as a banned AS from Spamhaus!
postfix-mailcow-1  | Using the open Spamhaus blocklists.
postfix-mailcow-1  | chown: cannot access '/usr/share/man/man1/mailq.1.gz': No such file or directory
postfix-mailcow-1  | 2025-07-18 10:14:31,498 INFO success: processes entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
postfix-mailcow-1  | 2025-07-18 10:14:31,498 INFO success: syslog-ng entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
postfix-mailcow-1  | Jul 18 10:14:33 1be0597f9620 postfix/postfix-script[373]: starting the Postfix mail system
postfix-mailcow-1  | Jul 18 10:14:33 1be0597f9620 postfix/master[375]: daemon started -- version 3.7.11, configuration /opt/postfix/conf
postfix-mailcow-1  | 2025-07-18 10:14:40,465 INFO success: postfix entered RUNNING state, process has stayed up for > than 10 seconds (startsecs)
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/postscreen[391]: cache proxy:btree:/var/lib/postfix/postscreen_cache full cleanup: retained=0 dropped=0 entries
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/postscreen[391]: CONNECT from [fd4d:6149:6c63:8a23::1]:47200 to [fd4d:6149:6c63:8a23::c]:25
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/postscreen[391]: ALLOWLISTED [fd4d:6149:6c63:8a23::1]:47200
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/smtpd[394]: connect from unknown[fd4d:6149:6c63:8a23::1]
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/smtpd[394]: TLS SNI mail.mydomain.tld from unknown[fd4d:6149:6c63:8a23::1] not matched, using default chain
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/smtpd[394]: Anonymous TLS connection established from unknown[fd4d:6149:6c63:8a23::1]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/smtpd[394]: lost connection after STARTTLS from unknown[fd4d:6149:6c63:8a23::1]
postfix-mailcow-1  | Jul 18 10:18:21 1be0597f9620 postfix/smtpd[394]: disconnect from unknown[fd4d:6149:6c63:8a23::1] helo=1 starttls=1 commands=2
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/postscreen[404]: CONNECT from [fd4d:6149:6c63:8a23::1]:51746 to [fd4d:6149:6c63:8a23::c]:25
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/postscreen[404]: ALLOWLISTED [fd4d:6149:6c63:8a23::1]:51746
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/smtpd[407]: connect from unknown[fd4d:6149:6c63:8a23::1]
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/smtpd[407]: TLS SNI mail.mydomain.tld from unknown[fd4d:6149:6c63:8a23::1] not matched, using default chain
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/smtpd[407]: Anonymous TLS connection established from unknown[fd4d:6149:6c63:8a23::1]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/smtpd[407]: lost connection after STARTTLS from unknown[fd4d:6149:6c63:8a23::1]
postfix-mailcow-1  | Jul 18 10:24:01 1be0597f9620 postfix/smtpd[407]: disconnect from unknown[fd4d:6149:6c63:8a23::1] helo=1 starttls=1 commands=2

I’d also like to note that I am using Traefik reverse proxy. I was having incoming traffic on all mailcow ports being routed through traefik, but I had noticed a log in postfix that was complaining it couldn’t do a DNS lookup on what looked to be a reversed local IPv4 (something like 5.1.168.192.com.some.sending.domain) of my reverse proxies IP so I allowed mailcow to handle incoming traffic (Opened the ports for mailcow instead of my reverse proxy, only letting traefik handle the webUI frontend) and those logs went away. I am still confused about why I am not getting emails however.

If my domain is needed for any troubleshooting I’d prefer to not let it be known on a public forum so if it is needed please give me an option to share it through a private DM of some sort.

Thanks for any help in advance.

ETNyx

If we will follow Occam’s razor, your problem is DNS,… Unless you will provide your domain name, I do not believe anyone will try help you.

Simile8008

ETNyx Is there any way for me to share it semi-privately, or is this going to be a situation where I have to post it on this public thread? I know that my domain is already inherently public just due to how the internet works, but I’m always a little paranoid about sharing it in the wrong place.

esackbauer

Your domain is already more or less public, as you have published MX records and running a mail server on port 25. every spammer can find it via portscan.
Post a PNG file of your domain name if you will….

ETNyx

May be short-lived, password protected pastebin suitable for you?

Simile8008

ETNyx That’ll work
https://pastebin.com/cMEXK0mK
PW: dweXe2w621

ETNyx

Basic DNS check seems fine, tried to send message to postamst@your-domain.ltd and got
Jul 19 16:47:07 86b50845bb8a postfix/smtp[2487]: F07924D15F: to=<postmaster@***>, relay=none, delay=30, delays=0.13/0.05/30/0, dsn=4.4.1, status=deferred (connect to ***[IP_OK]:25: Connection timed out)

so my server can’t reach your either, so some kind of firewall issue or if 25 is proxied error there,…

Also ping to your IP (A of your MX CNAME ending 32) does not work either, this may be on purpose blocked, but it’s diagnostic tool.

Also forcing SMTP to use IPv6 does not help,…

Simile8008

ETNyx That’s interesting. I wonder if something screwed up happened with my firewall then. I just tried pinging it myself from a different IP and got the same result. That should not be happening. I did update my OpenWRT router a few days ago. I will look into that and see if there’s a rule that is blocking pings somehow. I unproxied all the mailcow traffic from Traefik before I made the post. It should all be going directly to the mailcow containers now.

esackbauer

BTW you can test most issues like SMTP connection yourself:
https://mxtoolbox.com/SuperTool.aspx#

Simile8008

Okay, I’ve figured it out, and it was something I really was not expecting. When I had upgraded OpenWrt I did not realize at some point I had set it to automatically route traffic through a VPN. When it upgraded, it restarted making that rule to route all traffic through that vpn active. For some reason, this also appears to have applied to incoming WAN traffic. Removing that rule has made everything work again.

Also, just to put it out there I have a dual stack setup. I have SMTP set up for IPv4 and IPv6, but what I would assume happened, is because the VPN only has an IPv4 addr, IPv6 was unaffected, leading SMTP to show up as only supporting IPv6. This was a PITA to troubleshoot, but I thank you all for helping me out! 😃