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OT: blocking unauthorized senders

2006-12-13 14:13:38
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I apologize if this query would be considered too much of an off topic.

Anyway, here it is:

I am running several rather large aliases on our servers that are used as 
kind of listservs.  There was no problems with them till about a year ago 
when their addresses were harvested by spammers (probably from a laptop 
compromised during one of our researchers' travels) and spam started to 
arrive in large quantities.
As practically all addressees were local I used procmail to filter these 
spams away setting up several recipes to allow only local users the privilege 
to send mail to these aliases.
However, due to the pressure from the business administration, increasing 
number of external recipients started to appear on these aliases.  Of course, 
procmail being a point-of-delivery filter ignores these addresses and all the 
spam is happily delivered to external users.  The same applies for local 
users who setup forwarding to some outside addresses.

Hence my question:  Is there a way how to disable posting to these aliases 
from addresses (E-mail or preferably IP) that are not explicitly defined 
(allowed).

I would appreciate any nudge in the right direction.

Thanks


Frank Bures, Dept. of Chemistry, University of Toronto, M5S 3H6
fbures(_at_)chem(_dot_)toronto(_dot_)edu
http://www.chem.utoronto.ca
PGP public key: http://pgp.mit.edu:11371/pks/lookup?op=index&search=Frank+Bures
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