If a message has an attachment with a file name ending in a common executable file type - such as .lnk, .url, .exe, .reg, or .vbs - the entire message is rejected. This protects our users from malicious mobile code that propagates itself through email, as there is a history of defects in certain mail user agents whereby executable attachments can be launched without prompting the user or opening the containing message.

If you want to email executable files to someone at this system, it must be contained in some way as to keep it from being run without the consent of the recipient. For instance, one may rename an attached file from .exe to .xex, or one may place the .exe in some form of archive (e.g. a .zip file). In both examples, the recipient must explicitly act on the attachment before it can be launched, either to rename it back to its original form or to decompress it.

We believe that blocking directly executable file attachments is a reasonable and diligent countermeasure to unknown email-based malicious mobile code (virus, worms, Trojans, jokes, etc.). If you have any questions or concerns about our policy in regards to this matter, please contact the postmaster.