Rejecting and Renaming File Attachments

NOTICE: Due to the increase in sophisticated and destructive malware being delivered to computers through executable email attachments, UW-IT will reject all email messages that have risky types of executable files attached (such as .exe, .bat, .vbs and others). See below for more information on the types of files that will be rejected and alternative ways to share files safely.

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 silently discarded.
  • Messages with attachments of certain risky file types are rejected, which sends a notice to the sender that the message was not accepted.
  • Messages with an attachment with a ".zip" filename extension will be delivered but have the attached file renamed, unless they contain one of the risky file types, in which case they are rejected.

Action File Types Reason
Rejected — Messages containing one or more of the following executables, either directly attached or in a .zip file, are rejected with a notice being sent to the sender.

.ade .adp .bas .bat .chm .cla
.class .cmd .com .cpl .eml
.email .exe .hlp .hta .inf
.ins .js .jsp .lnk .msc .msi
.mst .ocx .pc .pif .reg .scr
.sct .shb .shs .url .vb .vbs
.vbe .wsf .wsh .wsc

On many computers opening these files will cause it to execute automatically and infect the computer. These file types are seldom used for legitimate communication, but are favored by malware writers.
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. .zip 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 destined for both on-campus and off-campus users sent through UW central email services, including UW (Deskmail) Email, UW Exchange, and UW Gmail, are included in this management practice.

Why Reject 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.

This type of rejecting is necessary with email because anyone can send email messages to anyone. In other words, anyone who wants to send you malware can do so.

Alternative Ways to Share Files

The way to share files safely is to place the file in a secure repository such as UW Google Drive or UW OneDrive for Business and then share the file with the specific person you want to make it available to. For example, you could place the file in a Google Drive folder and share that folder with the recipient. That way both you and the recipient have to authenticate (log in with your ID and password) to get to the file. Many such secure storage repositories are available.

More Information

Last modified: April 7, 2015