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Date: Mon, 2 Dec 1996 14:08:57 -0600 (CST)
From: Dave Bodenstab <imdave@synet.net>
Message-Id: <199612022008.OAA23152@base486.synet.net>
To: freebsd-questions@freebsd.org
Subject: Sendmail: can one block mail *to* certain domains?
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If someone could tell me if this is possible, and if so, where
to start, I'd appreciate it.

My problem is that my ISP has a customer for whom they queue email
until the customer dials in and connects.  The ISP uses dynamic
IP assignment, and with a hack, changes the routing for X.COM
to the IP# that they get assigned when they connect.  At this
point, all email destined for X.COM is routed directly to their
machine's sendmail daemon.

Unfortunately, when they disconnect, the routing of X.COM to
the IP# is sometimes not reset.  If I dial in and happen to
get the IP# that X.COM had, then suddenly my FreeBSD system 
gets all the email that has been queued for X.COM!  My system
then tries to forward the mail, but since the address lookup
for X.COM results in the IP# that I currently have, I get a
sendmail error "mail loops back to myself".  At this point,
my system returns the mail to the sender.  The load put on the
system by this activity is excessive, not to mention the
confusion that probably results to the senders.

I would like to reject any mail destined for X.COM.  I have 
seen solutions that block connections *from* certain domains,
but I don't want to block my ISP of course.  So, is it possible
to block email *to* X.COM before the email gets dumped to
my machine?  (My ISP knows about the problem, but they
haven't come up with a solution.)

BTW, I'm running the latest sendmail 8.8.3

Thanks,

Dave Bodenstab
imdave@synet.net