Unfortunately, viruses have become one of the worst problems on the internet. The "I Love You" virus (and it's more recent descendents) is credited with an incredible amount of damage. Sometimes this damage has been caused by the direct action of the virus (deleting files and such) and sometimes just by sending so many copies of itself that email systems crash and networks become unusable.
By now it should be obvious to just about anyone who has any contact with the internet at all that executable attachments should not be opened. Sometimes, however, it's not so obvious that an attachment is executable. For example, while most people would not open a .EXE file, they might open something with a filetype of .SCR. They might think this is a screen saver, for example. If the file appeared to be from a friend (because of a faked return address), then it would be easy to understand someone not even thinking about it.
One of the major reasons why I decided to install my own email server was to gain some additional measure of control over viruses. Of course I had Norton antivirus installed on each machine - that was only prudent. But there is one problem with antivirus software such as this: a time delay.
You see, viruses are created and then they propagate all over the internet. Some spread slowly (months or even years), and some spread quickly. Some spread like wildfire, leaping from system to system and spreading like a pool of spilled ink throughout the cyber world.
Since most people download new virus definitions on a weekly basis (that's the default update period for many products) there is a window of vulnerability between when a new virus hits and when the definitions to protect against it are installed. Even though I had our definitions set to download on a daily basis, I was still concerned about the small amount of time that our systems were vulnerable. Why? There is very little in the computer world that is more painful to recover from than a nasty virus infection.
I carefully studied several different email servers, and finally choose ArgoSoft Pro, mostly because it was easily the simplest, most configurable and most flexible system around (especially for the price).
I put a copy of Norton Antivirus for Gateways in front of the email server so that all email that my wife and I receive gets scanned for viruses before it hits our inbox. This means that email is received by the Antivirus program first, scanned, and then forwarded to the email server.
One thing that I did was to configure Norton Antivirus for Gateways to remove all attachments with an executable file type. This removal is done before the email is scanned for viruses. Basically, this means very few (if any) viruses are ever found: most of the newer ones are executable attachments and thus they are simply removed.
Some of the file types that I configured the system to remove are listed below. I have marked the .DOC and .XLS file types, as you might need to receive these for some reason (they are Word documents and Excel spread sheets). Note that this is only a partial list, but it does cover some of the most commonly received file types.
I know that all of this seems like a lot of work to set up and maintain, but believe me, it's worth it to not even have to worry about getting a virus. Those things can be nasty, and you don't want to catch even one, ever.