On Wed, Apr 06, 2022 at 02:41:04PM +0200, Matus UHLAR - fantomas wrote:
> >I think that you can stick with the default settings, which
> >keep connections open only when they can be reused immediately.
>
> this unfortunately did not work without listing destinations explicitly in
> smtp_connection_cache_destinations so I had big backlog of messages for
> those domains, even if I set smtp_connection_cache_time_limit=30 and
> enabled smtp_tls_connection_reuse...
What is your smtp_destination_concurrency_limit? Do you have working
inbound recipient validation? If you're relaying mail for many
subdomains, perhaps not, and the output congestion is a result of
delays in returning bounces to non-responsive or slow destinations.
You should look at "qshape -s" output to see whether there's a high
fraction of bounce mail in the backlog.
While, using "relay" for inbound mail will help to avoid inbound
delays due to outbound congestion, better still would be avoiding
output congestion.
Perhaps inbound probe-based recipient verification would help?
Or you might build a comprehensive recipient validation table?
Or otherwise determine why the congestion is happening.
--
Viktor.
