Postfix working with home network but not with USB 3G dongle

Question

Does postfix with php's mail command get configured during installation based on the network connection?

I am asking this because I installed it when I was connected to my home network. and I can send emails no problem. However, when I need to work remotely, and connect to the internet using a USB 3G dongle, I can no longer send out emails from php.

When I get back home, and connect to my home network, I can send emails via php perfectly again.

Answer 1

You can verify what the problem is by checking /var/log/mail.log immediately after trying to send an email.

My quess is that the 3g network you're using might be blacklisted, which would be understandable. This would result with emails being rejected by the destination email server and an appropriate message in the log file.