> I have several domains that I need to deliver for; and I use
> sender_dependent_default_transport_maps to map those to the correct IP's to
> send out of.
>
> I am experiencing a couple of related domains begin to defer our mail with
> with 450 and 421's.
>
> Aug 15 10:10:13 server postfix/smtp[27375]: B2A93E39647: host
> scc-mailrelay.att.net[204.127.208.75] refused to talk to me: 450 xx.xx.xx.xx
> has too many connections ( 3 ) on sccwmxc01
You can limit the per-destination concurrency with:
/etc/postfix/main.cf:
xxx_destination_concurrency_limit = 2
where xxx is the name of a mail delivery transport (first field in
master.cf).
Or you can just ignore the issue and let Postfix deliver the mail
on the next delivery attempt.
I have no quick solution for (per-sender source IP address) AND
(destination-dependent concurrency limit). If you need that amount
of control, then separate Postfix instances are required.
Wietse
