Spam and Malicious Email Filtering Policy


In a 2008 report, enterprise anti virus vendor Sophos reported that approximately 96% of all email is spam. In that same report they also state

"The figures show an alarming rise in the proportion of spam emails sent with malicious attachments between July - September 2008, as well as an increase in spam attacks using social engineering techniques to snare unsuspecting computer users. "

The University of Denver contracts with Microsoft to provide e-mail service for all student, staff, and faculty member e-mail accounts. E-mail messages pass through Microsoft Exchange Online Protection servers and are scanned for viruses. Because viruses and worms passed through e-mail as executable attachments are typically generated automatically and profusely by infected computers, e-mail messages found to contain infected attachments are discarded.

Microsoft has identified a number of attachment types that have, historically, been used to exploit computer operating system and application vulnerabilities. Microsoft Outlook will block these attachments. A complete list of blocked attachments can be found at the Microsoft Office Support site.


Do not open any e-mail attachment unless you:

  • Know the sender. Do not accept e-mail "candy" from strangers.
  • Confirm that the sender actually sent the attachment. Malicious messages may be disguised as coming from legitimate addresses. Do not open message attachments if you have any reason to suspect the authenticity of the message.


Please review the above warnings before opening any e-mail attachments.

People who need to transmit potentially malicious file types, may do so in several ways:

  • Senders can post the file on a website and tell recipients where they can download it. (This is usually the most appropriate method for distributing files to many recipients.)
  • Senders can rename the file before attaching it and provide recipients with instructions for changing the file name back to its original value.
  • Senders may encrypt the attachment or the message and provide instructions to decrypt it upon receipt.

Important: These techniques are sometimes used by criminals in an attempt to spread malware. The recipient should still heed the WARNINGS given above AND have up-to-date anti virus software installed and working on their system.


In addition to scanning e-mail for malicious attachments, Microsoft Exchange Online Protection also scans for harmless - yet unwanted - "spam" email. Email that Microsoft servers determine is spam will be delivered to your Junk E-mail folder. No computer system can perfectly predict whether you will consider a particular message to be spam. Some desirable messages will be delivered to your Junk E-mail folder and some spam will be delivered to your inbox. It is important that you periodically check your Junk E-mail folder for legitimate spam. Items in your Junk E-mail folder will expire after 29 days.


Last updated January 21, 2016