[exim] Attachment stripping...

     No matter how much we try and educated our users they insist on sending 
very large emails to all staff / student lists (and no management as the 
largest offenders wont allow up put limits on the list) .  We are considering 
stripping attachements over a specific size and replacing them with a unique 
URL pointing to the file, probaby a hash of the file contents which we could 
auto-expire after 6 months.  

    Has anyone done this already in Exim, or do I need to start from scratch..

Thanks,
    Ruairi