Mail server stopping to work

[bluenor]

Hi everyone. This morning I realized that the email I had configured and which was working, is no longer working. I tried to stop the firewall and I tried to send a message from my previously configured client but it can’t even connect to the SMTP server. The ports are open and the services are active. I also tried to access the webmail but that doesn’t work anymore either because it times out on port 20000. Below:

root@mail:~# systemctl status firewalld
○ firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/lib/systemd/system/firewalld.service; disabled; preset: enabled)
Active: inactive (dead)
Docs: man:firewalld(1)

root@mail:~# systemctl status postfix
● postfix.service - Postfix Mail Transport Agent
Loaded: loaded (/lib/systemd/system/postfix.service; enabled; preset: enabled)
Active: active (exited) since Sun 2025-02-16 07:10:41 CET; 17min ago
Docs: man:postfix(1)
Process: 1588 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
Main PID: 1588 (code=exited, status=0/SUCCESS)
CPU: 1ms

root@mail:~# systemctl status dovecot
● dovecot.service - Dovecot IMAP/POP3 email server
Loaded: loaded (/lib/systemd/system/dovecot.service; enabled; preset: enabled)
Active: active (running) since Sun 2025-02-16 07:10:37 CET; 17min ago
Docs: man:dovecot(1)
https://doc.dovecot.org/
Main PID: 803 (dovecot)
Status: “v2.3.19.1 (9b53102964) running”
Tasks: 4 (limit: 9470)
Memory: 5.7M
CPU: 79ms
CGroup: /system.slice/dovecot.service
├─803 /usr/sbin/dovecot -F
├─828 dovecot/anvil
├─829 dovecot/log
└─833 dovecot/config

root@mail:/var/log/virtualmin# ss -tuln | grep -E ‘:25|:143|:993|:110|:995|:10000’
udp UNCONN 0 0 0.0.0.0:10000 0.0.0.0:*
tcp LISTEN 0 1024 127.0.0.1:11000 0.0.0.0:*
tcp LISTEN 0 1024 0.0.0.0:10000 0.0.0.0:*
tcp LISTEN 0 100 0.0.0.0:143 0.0.0.0:*
tcp LISTEN 0 100 0.0.0.0:25 0.0.0.0:*
tcp LISTEN 0 100 0.0.0.0:110 0.0.0.0:*
tcp LISTEN 0 100 0.0.0.0:995 0.0.0.0:*
tcp LISTEN 0 100 0.0.0.0:993 0.0.0.0:*
tcp LISTEN 0 1024 [::]:10000 [::]:*
tcp LISTEN 0 100 [::]:143 [::]:*
tcp LISTEN 0 100 [::]:25 [::]:*
tcp LISTEN 0 100 [::]:110 [::]:*
tcp LISTEN 0 100 [::]:995 [::]:*
tcp LISTEN 0 100 [::]:993 [::]:*

The only operation that has been done that I know of is the update of virtualmin via apt command.

I can’t find logs for debug, anyone can help me to understand what happening?

SYSTEM INFORMATION
OS type and version	Debian 12
Virtualmin version	virtualmin-core 7.0.0

[Joe]

This is multiple unrelated issues. Webmail on port 20000 is Usermin, which is unrelated to any mail server stuff. So, make a new issue for the Usermin problem.

It is possible your hosting provider blocked port 25. If your system was sending spam (whether intentionally or through an exploited web app or something), it’s pretty likely.

Postfix has two units on Debian (for reasons that don’t make sense), the one that’s actually providing service is postfix@- so look at that one.

[bluenor]

Thank you for your prompt reply. As soon as you sent it to me, I immediately opened a ticket with my provider, who confirmed that they had infrastructural problems on their network. I was wrong not to run a tcpdump. I was misled by the fact that there had been an update to webmin and virtualmin and that the main virtualmin and apache ports were working correctly with their services. Apparently during this infrastructural disservice some ports worked and others didn’t. It’s very strange though. I’ve finished the last tests now and everything seems to be working. I don’t know how to thank you for the quick response. As always, it gave me some useful food for thought to solve the problem.

[ID10T]

@bluenor

Apparently during this infrastructural disservice some ports worked and others didn’t.

Sounds like they had a firewall problem. Kind of the last thing you’d expect though was that some ports worked and others didn’t when it was working previously. Starting with the latest changes on your machine wasn’t a bad place to start looking though. Kinda of the logical thing most people would do.