First, yes you can change this to allow just about any type of attachment, however I'm not going to tell you how just yet...
The reason we limited the file types to .TXT, .TIF and .BMP are because they are light to render (or already rendered in the case of TIF) and, as such, will have a minimum impact on the voice server. Since in an ActiveFax configuration the fax server is on our box we have to be very careful about not letting the rendering engine step on the CPU since it'll slow the conversation down... that would be bad.
If you're running a 3rd part fax or you're running ActiveFax in a 2 box configuration (in Unity 2.4) you can expand the list of attachments the fax server will be sent, of course. But you'll need to be careful since most fax servers I've tested are NOT smart about dealing with wierd attachments like .DLL or .EXE files. They will fail the fax entirely or, in a couple cases, choke and stop working period.
Also, you will need to install an application that can handle the attachments on the box (another reason why ActiveFax locks this down, we don't want Word and Excel etc... installed on the Unity server). Most fax servers use OLE rendering to rasterize these attachments (VERY CPU intensive) and this requires the application in question to be available on the box.
Short answer, yes you can change this in some cases, but proceed with caution. If you have a two box configuration, let me know and I'll cough up the procedure to expand the allowed extensions through.
Jeff Lindborg
Unity Product Architect
Active Voice Corp
jlindborg@activevoice.com
