[Mimedefang] Verifying mailbox...

[Ashley M. Kirchner]

    Our mail setup at work consists of several machines, hosting several 
domains:

     __________
    [          ]       [ MX running ]       [   mail spool   ]
    [ INTERNET ]  ---> [ mimedefang ]  ---> [ with mailboxes ]
    [__________]       [   and SA   ]       [                ]

    However, there are more than one mailspool, and incoming mail gets 
directed to the appropriate spool based on the recipient's domain and 
sendmail's mailertable file.

    The problem I have is with these dictionary attacks, where mail 
would come in to many invalid users at one of the domains.  It hits the 
MX, and while some gets bounced, some don't (because I still don't 
believe bayes is doing jack squat on my end - that's a different 
story.)  So, assuming one of those attacks gets past mimedefang, the MX 
then tries to deliver to the mail spool, only to have the mail spool 
return a user unknown.  At that point, that piece of email gets 
forwarded to the postmaster of said domain (after all, as far as the 
spool is concerned, it came from the mx, not from whatever the outside 
source was.)

    So, my question now is, from within mimedefang, is there some way I 
can have it validate a recipient's address PRIOR to attempting 
delivery?  Like somehow contacting the spool and see if that user 
exists, and if not simply bounce the message before it even gets onto 
our network.


-- 
W | I haven't lost my mind; it's backed up on tape somewhere.
  +--------------------------------------------------------------------
  Ashley M. Kirchner <mailto:ashley at pcraft.com>   .   303.442.6410 x130
  IT Director / SysAdmin / WebSmith             .     800.441.3873 x130
  Photo Craft Laboratories, Inc.            .     3550 Arapahoe Ave. #6
  http://www.pcraft.com ..... .  .    .       Boulder, CO 80303, U.S.A.