Here are the IMAP settings for the new TAMU Email in Thunderbird. This is how I have mine set up.
Server Name: email.tamu.edu
Port: 993
User Name: <your email user name>
Use secure connection: SSL
For your outgoing SMTP server:
Description: <whatever you want to call it>
Server Name: smtp-relay.tamu.edu
Port: 587
User Name: <your email user name>
Use secure connection: TLS