[Mailman-Users] Dealing with rate limiting from Roadrunner/Time Warner

Stephen J. Turnbull stephen at xemacs.org
Sat May 17 09:08:10 CEST 2014

Conrad G T Yoder writes:
 > On May 15, 2014, at 8:48 PM, Stephen J. Turnbull <stephen at xemacs.org> wrote:

 > > The log you display is not a true bounce.
 > Gotcha.  I guess someone thought it was a true bounce and
 > configured their servers appropriately. :^) 

Could be.

The other possibility is that you have enough Roadrunner subscribers
that when a post goes out, one connection gets through, a bunch get a
temporary fail and requeued.  4 hours later, your MTA tries a bunch
and one gets through.  A bunch minus 1 get a temporary fail, and
requeued.  8 hours later, your MTA tries a bunch minus 1 and one gets
through.  A bunch minus 2 get a temporary fail, and requeued.  This
happens up to 5 times with approximately exponential backoff.  If the
5th retry fails, it will be considered a permanent failure (by your
MTA).  So if "a bunch" is bigger than 5, you'll get "true bounces".
If any of these retries overlaps with a new post, the problem gets
compounded.  (All the concrete numbers depend on your MTA's
configuration, but they're pretty typical, I believe).

At this point, it should be clear why I consider Roadrunner's policy
to be braindamaged.  They're wasting your resources and DoS'ing their
own users.

BTW, it should be possible to reconfigure your Mailman and MTA so that
Mailman sends the maximum number of addresses per SMTP connection (for
this you need to turn personalization OFF) permitted by Roadrunner in
one shot, and the MTA does as well.  It may be possible to get your
MTA or Mailman to sequence contacts to Roadrunner so that only one
SMTP connection is open at a time.  Maybe Roadrunner will tell you
what the relevant numbers are, or even give you a higher limit.

Nevertheless, as long as they have this policy, the possibility of a
retry cascade exists.  And the numbers that Roadrunner offers may be
much smaller than your MTA's optimal configuration from your point of

 > I have not yet tried the nuclear option - the infamous EECB
 > (Executive Email Carpet Bomb).

Bu-wha-ha-ha-ha!  But I hope things don't go that far.


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