I'm dealing with a setup, where I need to be able to send notification mails from clients in different subnets, but the mailserver is only accessible on one of them.
I've setup a machine which is multi-homed in all available networks, and also has alias-IPs for shared physical networks. Let's call it "Babylon".
The plan is to use sSMTP on Babylon, to forward it to the local mailserver.
It works to send mails locally on Babylon, but when I try to send mails from another machine through Babylon, I get the following error:
[SOLUTION]send-mail: Cannot open babylon.office.local:25
Can't send mail: sendmail process failed with error code 1
Well, sSMTP can't relay, so it won't listen on SMTP-ports.
Had to use Exim4 instead.