On Fri, Mar 19, 2010 at 03:58:42PM +0100, Attila Nagy wrote:

> I have a somewhat busy mail relay running postfix 2.7, which has problems 
> with a slow destination.

> I can't limit the number (or rate) of incoming e-mails for that domain, and 
> I can't increase the throughput of the destination, because I don't operate 
> it (OK, that may be false, because postfix's destination concurrency 
> adjusments can make it worse than what it could accept).

Forward mail for this domain to a separate queue (Postfix instance)
that handles mail for this---and perhaps some other similar---domains.
The slow domain will no longer clog your primary queue.

Happy spamming...

> And this is one for citromail:
> Mar 19 15:47:47 mail postfix/smtp[33147]: 28E47768F4: to=<@citromail.hu>, 
> relay=server03.citromail.hu[91.83.45.3]:25, conn_use=76, delay=9538, 
> delays=5062/4475/0/0.33, dsn=2.0.0, status=sent (250 ok 1269010067 qp 
> 29585)

The latency of "0.33" seconds is not unreasonably high. Is this typical
for deliveries to this domain? With a concurrency of 20, you should be
able to deliver ~60 messages per second to this destination. Can you
compute a "smoothed" latency for this destination?

        initialize:     lavg := 0;
                        count := 0;

        step:           lavg := lavg * 0.95 + (c + d) * 0.05;
                        count := count + 1
                        if (count % 100 == 0)
                                println lavg;

The "c" and "d" values would be the sum of the connection and delivery
delays in the log entry.

        delays=a/b/c/d, ...

How many concurrent connections do you have for this destination?
What is the destination concurrency limit?

-- 
        Viktor.

P.S. Morgan Stanley is looking for a New York City based, Senior Unix
system/email administrator to architect and sustain our perimeter email
environment.  If you are interested, please drop me a note.

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