On Tue, Mar 18, 2003 at 01:27:28PM -0800, Ronald F. Guilmette wrote:
P.S. Recently, a couple of major ISP... specifically AT&T and RoadRunner...
tried, and failed, in implement filtering of IP addresses that have no
reverse DNS. The problem in both cases was that this change created far
too many complaints, once it was first switched on, from the respective
customer bases.
At the University of Minnesota, we have been blocking email from an
ever-increasing number of sites which have no valid rDNS. Our approach
was to do this selectively, based on IP networks, adding new ones over time.
Presently we require rDNS for 172 class A networks (granted, many of
these are reserved IP space) and countless class B and C networks.
Last week we blocked 6% of our incoming mail in this way with very few
complaints. It probably helps that outside users have a means of
requesting block exceptions from our users (via URL), which they can
grant or deny.
--
Steven F. Siirila Office: Lind Hall, Room 130B
Internet Services E-mail: sfs(_at_)umn(_dot_)edu
Office of Information Technology Voice: (612) 626-0244
University of Minnesota
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