For months I've been using a 5g sprint card for my laptop to check email. I have gmail, and three other accounts all configured in Thunderbird. Recently, I got AT&T internet service at my house and I discovered that I cannot send email when connected to my home service. I can receive just fine, but I can't send. If I plugin my 5g card, I can sent/receive with no problems.
At home I'm connected wirelessly through a router. What could be causing this interruption? I even tried pinging my smtp server only to see it timeout when connected via AT&T. If more details are needed, I'll be happy to share.
Correction: Sending through Gmail's smtp works. What types of things should I look for to diagnose the issue?