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Blocking and Renaming File Attachments

Blocking and Renaming File Attachments

Processing Email with Attachments

Most files attached to email messages are of little risk and they are delivered. However certain types of attached files trigger these special processes:

  • Messages with attachments determined to contain a virus are blocked.
  • Messages with attachments of certain risky file types are blocked or rejected.
  • Messages with an attachment with a “.zip” filename extension will be delivered but have the attached file renamed.
Action File Types Reason
Blocked — Messages containing attachments of these types are discarded. No warning is sent to either the sender or the recipient.

.cmd, .com, .cpl, .hta, .pif, .scr, .bat, .vbs

These file types are seldom used for legitimate communication, but are favored by virus writers. On some computers opening one of these files will cause it to execute automatically and infect the computer.


Renamed — Email messages containing attachments of these types have the attachment renamed by the UW central email services. The text “-UWunsafe” is appended to the original file name.


This file type is used by virus writers to circumvent antivirus programs, but may be used for legitimate purposes.

What Email Does This Apply to?

All email processed by the UW central email services, including email destined for off-campus users, is included in this management practice.

UW Information Technology will monitor changes in threats from attached files and add or drop types of files from the blocked or rejected list as needed.

Why Block These Attachments?

Email attachments are a common method for computer viruses to spread. Virus infections can cause serious problems both for the computer user and the UW email system.

More Information

About Viruses and Attachments

  • Security

Last modified: June 26, 2013