Update: Many issues seem to be resolved.
Because of compromises caused by Virginia Tech affiliates responding to phishes or clicked malicious links, and resulting in compromised machines, email sent from Virginia Tech is being blocked or “blacklisted” by several companies and organizations, including many EDUs. You may receive “bounceback”, “denied”, or “delayed” error messages when sending an email even though a similar email was sent previously. The email may contain a return message with wording similar to: “554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.” Currently Virginia Tech is definitely still being blacklisted by AOL, Hotmail and other .EDU's.