[unisog] hop counts and bounces on unisog list

Russell Fulton r.fulton at auckland.ac.nz
Wed May 12 01:17:03 GMT 2004


Hi All,
	We have had a bunch of cases (at least a dozen) over the last few days
of people being unsubscribed from the list because of excessive number
of bounces.  On investigation it would appear that most of these bounces
are being caused by exceeding the hop count limits.  Further
investigation reveals that some of the posts that are causing the
problems mine <Russell crawls away into a dark corner>. 

Here is what I believe is happening
     1. Due to two lots of AV checking :( (and other idiocies that I
        won't bore you with) the hop count is 7 when it leaves our mail
        system.  This will change soon but while I'm on leave sending
        stuff from outside the campus I'm stuck with it.
     2. I was sending to unisog at sans.org rather than
        unisog at lists.sans.org which adds another couple of hops
     3. normal processing at SANS adds 5 hops 
     4. default sendmail hop limit is 17 (so out MTA people tell me)

so if you have a significant number of hops to process mail at your end
then you can exceed the default sendmail hop count resulting in a
bounce.

For my part I'll be using lists.sans.org in the hope that this will
reduce the problems from my posts but I think it would also be a good
idea for folks to raise the hop count from the limit of 17 on sendmail
installations (postfix defaults to 50).  

What has changed is that mail system are because of anti spam and anti
virus checking which can add a couple of hops to a message.  When this
happens at source, when going through a mailing list system and again at
destination hop counts balloon out considerably.

Cheers, Russell 
-- 
Russell Fulton                                    /~\  The ASCII
Network Security Officer                          \ /  Ribbon Campaign
The University of Auckland                         X   Against HTML
New Zealand                                       / \  Email!





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