Have you checked with the support guys from the college? Maybe you have their outgoing server correct, but need to turn on authentication or use a different outgoing port that 25. I know with my local isp they use different ports incoming and outgoing that your standard 110/143 or 25.
Might be worth looking at if they have exchange to setup a rule that says anything incomming to
user@college.edu forwards to
you@gmail.com.
I just my gmail account for everything, Easy to setup for the pro.