How to block an outgoing e-mail if it is positive to anti-virus scanning

Hi all,


it is a while I am looking for a way to block infected outgoing e-mails from 
being sent (I don't want to send them intentionally of course, but you never 
know what's in the attachments: so I scan all my e-mails, including outgoing).

I successfully scan (and locally sort accordingly) infected incoming e-mails 
by using /usr/bin/kmail_clamav.sh.

In simple steps, I wish it'd be possible to:

1) write an e-mail and attach it a file;
2) scan it while it's being sent;
3) if positive, stop it and copy it to a local folder.

I can complete step 1 ;-) and 2 (I configured a filter so to scan all outgoing 
e-mails) but, regarding step 3, I don't know how to stop the mail if it is 
positive (I can of course copy it to a local folder).

I even opened a discussion on kdeforums* but haven't received any reply yet, 
so I apologise if the issue has been already discussed. If yes, please point 
me to the relevant resource, if not every suggestion would be appreciated.


Regards,
Antonio


* http://forum.kde.org/viewtopic.php?f=20&t=83619