(Joel Snyder, TechTarget) Some email managers have asked for the ability to stop certain types of files from coming through the system. The premise is simple: some types of files are rarely legitimately sent. A good example would be a file with an extension of .BAT. Yes, IT people do occasionally and legitimately send .BAT files. But all of the non-IT people in an organization should not be getting .BAT files. And if they do get .BAT files, then they are probably getting into trouble with them.

This leads to a lot of antivirus configurations that delete certain body parts from email messages. Good products let you do this in three different ways:

1. By the filename of the body part (such as *.mp3)
2. By the MIME label (such as MIME type "audio/mpeg")
3. By the fingerprint of the file as detected by the email gateway (such as "audio files").

A key consideration: The only reason to look at types of email body parts is to block them from entering your organization. Don't use these features to exempt certain types of data files from virus scanning. Remember: Computers are cheap, people are expensive, and (more importantly) attackers are constantly moving their attack vectors. Any attempt to optimize your antivirus configuration to speed performance is going to eventually compromise security.

Blocking certain types of files from entering via email is more of a business-by-business decision. Going one way or the other can't be classified as a best practice.