postfix smtp "Network is unreachable"

[Judman13]

Hello,

In my syslogs I am seeing proxmox attempt to send out emails, but it fails because the "network is unreachable". The problem is I cannot find the configuration file to correct or stop the issue and really I do not know what is triggering it.

This only shows in one of my two cluster nodes:

Sep 11 01:06:01 pro600 postfix/qmgr[943]: C0B73160EBD: from=<root@pro600.domain.org>, size=32609, nrcpt=1 (queue active)
Sep 11 01:06:31 pro600 postfix/smtp[1743168]: connect to hosted.mailcow.de[5.1.76.202]:25: Connection timed out
Sep 11 01:06:31 pro600 postfix/smtp[1743168]: connect to hosted.mailcow.de[2a00:f820:417::202]:25: Network is unreachable
Sep 11 01:06:31 pro600 postfix/smtp[1743168]: C0B73160EBD: to=<judson@domain.org>, relay=none, delay=349118, delays=349088/0.01/30/0, dsn=4.4.1, status=deferred (connect to hosted.mailcow.de[2a00:f820:417::202]:25: Network is unreachable)

 

[BobhWasatch]

Are you sure your ISP allows outbound connections on port 25? It is pretty common to block that as an anti-spam measure. Maybe try to connect to your mail host manually using telnet or netcat to verify.

If port 25 is blocked you will need to use the submission port, 587. That generally uses TLS and requires authentication. Your mail provider should have documentation on how to do this.

Or use your ISP's mail server as a forwarder.

 

[Judman13]

Are you sure your ISP allows outbound connections on port 25? It is pretty common to block that as an anti-spam measure. Maybe try to connect to your mail host manually using telnet or netcat to verify.

If port 25 is blocked you will need to use the submission port, 587. That generally uses TLS and requires authentication. Your mail provider should have documentation on how to do this.

Or use your ISP's mail server as a forwarder.

I don't actually want to use the email. I do not know when or how it got configured and I cannot figure out how to turn it off haha.

 

[BobhWasatch]

You probably have undelivered mail from when it was configured. Check in /var/spool and /var/mail.

I'm not able to access my PVE right now but would suggest you review the PVE manual about notifications:
https://pve.proxmox.com/pve-docs/pve-admin-guide.html#chapter_notifications

Or maybe you could uninstall postfix if you don't need it.