Since you don't have a valid domain name, send mail from your machine using your own email address as the reply. Gmail might not think it's legitimate mail coming from the college saying it has a return address as gmail.
Test Thunderbird by reading mail from the imap server on your own machine. Pick either mbox or maildir format for your mailbox format. Look online to compare the two. mbox is easier.
Basically you should be able to send mail from your machine and read mail on your machine.
Try using Squirrelmail to login from another machine in the lab and using the web based system.
If you are interested, try setting up in the transport file to deliver mail to another machine in the lab. Now you can mail from machine to machine.