[Mailman-Users] Odd smtp-error

Brad Knowles brad at stop.mail-abuse.org
Sun Oct 24 15:09:43 CEST 2004

At 12:41 AM -0400 2004-10-24, Rich West wrote:

>  So, I guess it is a toss up as to having VERP enabled with one SMTP
>  connection per transaction or disabling VERP and setting the SMTP max
>  sessions per connection to 0 (unlimited)...
>  Recommendations/suggestions? :)

	It's a classic performance versus ease-of-administration 
trade-off.  VERP definitely makes it a lot easier to properly 
administer mailing lists, and you can pretty much guarantee that no 
matter what the user might do on their end, if you get a bounce back 
to a given VERPed address, you can figure out what the original 
recipient was and remove them from the list.

	But there is a performance cost to using VERP.  You need to 
decide whether or not that is worthwhile in your case.  I think the 
FAQ entries should be able to help you figure out what the cost might 

	Now, the truly weird thing is that you shouldn't have to limit 
the number of sessions per connection with sendmail.  No version of 
this program in recent history (like the last five ten years) should 
have problems with the kind of thing you're trying to do.  Either 
you've got a truly ancient version of sendmail, a version of sendmail 
that is configured in an extremely strange way, or something else is 
going on that you're not aware or or not telling us.

	Could there be a firewall between you and sendmail which might 
impact what happens during the SMTP transactions?  I know that cisco 
PIX firewalls are known to break SMTP in some strange ways, and I 
wouldn't be surprised if there were other firewalls that did 
something equally strange.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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