No emails are being sent

[bnachbauer]

Hello,

I am running version 8.3.2 on Ubuntu 24.04.3. It is newly installed, but I restored a backup (same version) to change hosting providers (VM OVH -> other VM OVH).
My problem is that no emails are being sent.
In the logs, I have several types of messages:

• Tried all MXs
• DNS lookup failure: Error: queryMx ESERVFAIL

On the forum, I found a similar case that allowed me to identify what I think is an anomaly:

toto@cloudron:~$ host -t MX gmail.com 127.0.0.1
;; communications error to 127.0.0.1#53: connection refused
;; communications error to 127.0.0.1#53: connection refused
;; no servers could be reached
toto@cloudron:~$ systemctl status unbound
● unbound.service - Unbound DNS Resolver
     Loaded: loaded (/etc/systemd/system/unbound.service; enabled; preset: enabled)
     Active: active (running) since Tue 2025-11-11 18:02:32 UTC; 14h ago
    Process: 9903 ExecStartPre=/usr/sbin/unbound-anchor -a /var/lib/unbound/root.key (code=exited, status=0/SUCCESS)
   Main PID: 10033 (unbound)
      Tasks: 1 (limit: 9434)
     Memory: 8.4M (peak: 8.8M)
        CPU: 342ms
     CGroup: /system.slice/unbound.service
             └─10033 /usr/sbin/unbound -d

Notice: journal has been rotated since unit was started, output may be incomplete.

Do you have any idea what might be causing this problem and how to fix it?
Thank you.

[bnachbauer]

I just found a solution, but I'm not sure if it's very clean:

• In /etc/unbound/unbound.conf.d/cloudron-network.conf, I:
  -- added interface: 127.0.0.1
  -- disabled IPv6: do-ip6: no
• In OVH's Edge Firewall, I authorized all UDP

[joseph]

@bnachbauer For DNS,

127.0.0.53 - systemd-resolved of default ubuntu runs here
127.0.0.150 - cloudron's internal DNS (unbound) runs here. this is also used by mail server.

There is nothing running on 127.0.0.1 out of the box. The forum post you saw are obsolete. I think what fixed it was opening the UDP firewall required for DNS to go out. I think you can remove the interface: 127.0.0.1 line.

[bnachbauer]

I confirm. It work without 127.0.0.1