suggestions for blocking dangerous mail attachments?

[Juan Mejia <jmejia () uchile cl>]

Hello guys,
    Tired   of   users  who  refuse  to  think twice before running an
    attachment,  I  thought  that  it  would  help  if  the  mail  was
    downloaded  from  the  institutional  server  to  a box that would
    process    it   and  change  dangerous  file  extensions  in  the
    attachments  to  something  like  "Don't  run/rename  if not sure"
    (maybe  "format.com.DRIS").  Yes,  people still can run the files,
    but  first  they would have to save and rename them. This makes it
    harder   to   execute   a  file,  avoiding  the  fast,  thoughtless
    reaction of double clicking anything they see on the screen.

    Ok,  googling  the web I found that ashampoo  mail  virus  blocker
    does  this  (do  I  need  to say I expected this to be an original
    idea),  the  problem  is  that  I  would  prefer  a single machine
    processing  the  20+ mail accounts. Although I don't know how, I'm
    pretty   sure this can be done on my learning-toy-experiment-spare
    Linux box.

    Here are my questions:

         What's your opinion about changing file extensions on windows
         machines to reduce the threat of malware through e-mail?

         Do you know of some application that does this on linux?

         If  there's  nothing  like this on linux, what should I start
         reading,  searching,  etc.  in order to make it on my own? (I
         have   no   idea   about  e-mail  on  Linux. Also I realize I
         probably   will   never get to do it, but having a project in
         mind  is the best way to learn  about something new).

Thanks in advance,

 Juan                          mailto:jmejia () uchile cl