[Mimedefang] $helo filter checks

[Ole Holm Nielsen]

I tried the filter_relay subroutine suggested by John Halewood in
http://lists.roaringpenguin.com/pipermail/mimedefang/2003-October/017812.html,
changing the IP-addresses 195.166... and the domain example.com in
the script to accord with our network.  I also set MX_RELAY_CHECK=yes
in /etc/sysconfig/mimedefang and restarted mimedefang.

Based on some 12 hours of operation, I'm really pleased with the
rejections based on the rules in John's filter.  We've rejected
a number of spams on account of both bad HELO and spammer IPs
claiming to be our server.  IMHO, something like John's
filter_relay ought to be part of the MIMEDefang distribution's
example mimedefang-filter script.

Ole Holm Nielsen
Department of Physics, Technical University of Denmark,
Building 307, DK-2800 Kongens Lyngby, Denmark