[Mailman-Users] Increasing the Speed of Email Delivery

[Bernd Petrovitsch]

On Don, 2009-12-17 at 17:04 -0800, Carl Zwanzig wrote:
> Lots of it depends on the MTA (general opinion is that postfix seems to be 
> the fastest), connectivity, and list settings (personalized email will take 
Do I take the flame bait?;-)

Whatever you understand in detail under a "fast MTA" (and even if it
would be the case), it doesn't really matter IMHO because
a) Email/SMTP never was anywhere near "realtime" (though many people
   expect mails to be delivered in seconds),
b) if your local Internet connection is too small, it doesn't help to
   have the fastest MTA[0],
c) the local MTA resolves various hostnames and that could be "slow" and
   will involved timeouts (where every MTA out there just can wait)[0],
d) if your hardware (RAM, disks) are too small or slow, the MTA really
   can't do anything (and I expect all widespread MTAS to reasonably
   minimize the I/O and memory anyways). That may be irrelevant on the
   usual small mailserver with average nowadays hardware but if you have
   e.g. a small ISP with >25K mailboxes and (on the average) 1E6 mails
   per day ("after" using DNSBLs blocking lots of spam/viruses before
   even sending "EHLO"), it
   looks quite different,
e) b) for the remote MTA - but you have absolutely no influence on the 
   remote side[0],
f) c) for the remote MTA - but you have absolutely no influence on the 
   remote side[0],
g) the remote MTA may do extensive spam/virus checking, grey-listing,
   ... - taking time - causing "slow" mail delivery you have absolutely
   no influence on the remote side[0].
Of course the timeouts and waiting from above cost next to no
resources/performance locally (so the MTA(s) usually deliver several
emails in parallel without any problems as long as the box(es) do not
trash) but it costs total time (which makes email delivery "slow").

So I don't think that saving 10% (or even 50%) local "speed" will make a
significant difference (perhaps if you have a *really* large setup - but
even then deploying one more box is cheaper than investing a day to
improve the local performance. OK, saving a box is better for the world
as such ....).

	Bernd

[0]: And changing the local MTA won't solve that.
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