1) You can set up your Time Away Responder to say "My e-mail's not working right now! Call if it's urgent."
2) You can set up mail forwarding to send your mail somewhere else in addition to your postoffice account, such as a free Gmail account.
You can of course send mail that appears to be from your Cornell address, even if you're not sending it through a Cornell server.
And, don't forget today is Firefox Download Day 2008!