On 2/22/2011 11:44 PM, Robert Goodyear wrote:
On Feb 22, 2011, at 9:06 PM, Noel Jones wrote:
On 2/22/2011 9:29 PM, Robert Goodyear wrote:
The postfix connection caching algorithm will automatically limit the damage
caused by a subset of slow-responding relayhosts.
I suppose there's a tipping point of how much it would queue in memory versus
paging it off to disk, right? Or would, for example, our friends at (name your
favorite ISP here) decide to greylist us and just saturate the deferred queue
such that the subset becomes the majority? In other words, is Postfix's
algorithm written to prevent exclusive saturation by reserving some percentage
of its allocated limits for !=(grouchyISP)
That was referring to mail for a single destination, such as a
relayhost farm. For general high-volume internet delivery,
it's generally recommended to have an internal fallback_relay
or two that collects mail that can't be delivered right away.
This keeps the defer queue low and keeps slow/dead
destinations for hogging the active queue. This is covered in
the docs referenced earlier.
I just had a thought, however... I wonder if I can mess with the backoff
behavior of my edge MTAs to tell my origin server to cool it a bit in response
to its (the edge's) workload? Will MX parity cause Postfix to hear the backoff
request and move on to another equally-weighted server, or will it just defer
the message and mark it as being destined for the exact same server that it
handshook with and got the backoff request from?
Postfix does not remember the last host tried for a
destination, and looks up the MX each time the message is
scheduled for delivery. Most of the grouchy ISPs have some
sort of registration program for high-volume senders so you're
not throttled or blacklisted.
The default settings should give very good performance. For knobs to twist,
please see:
http://www.postfix.org/TUNING_README.html#mailing_tips
http://www.postfix.org/QSHAPE_README.html
http://www.postfix.org/QSHAPE_README.html#backlog
-- Noel Jones
Thanks for those links. It's easy to get bogged down in theory and not RTFM
from the top again.
