On Fri, Apr 01, 2011 at 09:20:39AM +0200, Ultrabug wrote:
> > What happens if you happen to exceed the limit on particular host
> > among the 10? If it just quickly returns a 4XX code, and does not
> > penalize future connections, ignore this limit and let Postfix do
> > what it does by default.
> >
>
> The result is pretty much that they deny any further email with 4XX
> codes AND penalize further connections. It just stops accepting any new
> mail.
So instead of gently nudging you to the right sending rate, the DoS
their service and require the whole planet to hand-tune transports for
their domain, this is insane, and as much as possible, senders should
not play-along with this insanity. I know that some senders will have
to jump through hoops for business reasons, but if possible apply some
spine.
> > Have you considered the less aggressive concurrency
> > feedback controls in Postfix 2.5?
> >
> > slow_initial_concurrency = 2
> > slow_destination_concurrency_limit = 15
> > slow_destination_concurrency_failed_cohort_limit = 5
> > slow_destination_concurrency_positive_feedback = 1/5
> > slow_destination_concurrency_negative_feedback = 1/8
> >
>
> This sounds interesting indeed, I didn't understand fully these
> cohort/feedback options, I'll give them a try !
This really won't help if the remote sites response to exceeding their
maximum rate is a sticky refusal to accept further mail.
If that's the case, you must psychically (i.e. prior hand-tuning) stay
under their limits. The feedback controls assume that the feedback is in
the form of transient 421 responses when the connection concurrency or
re-use limits are reached. No simple feedback algorithm will dynamically
adjust to a feedback control that goes from open to sticky-closed.
> > and if absolutely necessary, in master.cf:
> >
> > slow unix - - n - - smtp
> > -o smtp_connection_reuse_time_limit=30s
> >
> > (the remote side starts rejecting traffic consistently instead of
> > sending 421 for the 100th RSET over a given connection).
>
> Many tanks for your time and help
You probably can't do much with my advice, when the receiving system
is fubared, your options are limited.
--
Viktor.
