[imp] Is it possible to filter out specific mime type attachements

[Aero Controls, Inc.]

We have installed Imp 3.1 and we would like to disable the ability 
for a user to download specific mime type attachements (ie, exe's, 
zips, scr, etc) you know those that have the capacity to contain 
malicious code.

In the webmasterworld.com forum I started a discussion about this and 
there was input back that in version 2.1 there was a mime.php file 
that you could ammend to disable the the download. But in this 
current version I do not seem to be able to locate the section that 
would allow us to do such a thing. Could some one point me in the 
right direction.

Thanks