We initially sent this announcement to the O365-SIG list and decided to send it to the broader IT community:
This morning, our email message sanitation vendor had a service-wide problem with their virus definitions. This is widespread and not specific to Penn.
Due to this issue, many emails got quarantined, even though there were no viruses present in the emails. Additionally, as the messages were quarantined, an annotation was added to the email subject: [Virus Error].
The vendor has fixed the issue, and ISC is in the process of releasing all mail that was erroneously quarantined in the order it was received. We expect that this will take up to an hour. Please ignore the annotation on the subject line for emails received today.
We apologize for the inconvenience and thank you for your patience and understanding.
If you have any questions, please contact Client Care online at http://supportcenter.upenn.edu, by email at help@isc.upenn.edu, or by phone at 215-898-1000.