I sent an email to somebody with an hotmail.com address.
It gets bounced with a:

     host mx3.hotmail.com [65.54.188.72]: 550 SC-001 (BAY0-MC1-F4) Unfortunately, messages from 35.9.75.106 weren't sent. Please contact your Internet service provider since part of their network is on our block list.


I am assuming that 35.9.75.106 is an mail.msu.edu address.

Did anybody experienced something like this before. What should I do? I 
need to reply to that email.


-- 
Oscar Castaņeda
Global Observatory for Ecosystem Services
Michigan State University