Disable port 25

[Koda]

I have config Gotify and disable the default rules and mail notification.

PBS try allways connect to port 25. how can I disable this?
I don't found any settings for this connection

 

[UdoB]

Well, if you really do not want to send (or receive from "local") emails then you might disable the local MTA, postfix:

 systemctl status postfix; systemctl disable --now postfix; systemctl status postfix

Disclaimer: not tested - I am using it intensively and my recommendation -of course- is to actually use it as intended... ;-)

 

[Koda]

My problem is not primarly the used port, but the gotify Message "Undelivered Mail Returned to Sender"
But I think this help me. thank you