Forwarders and mailing lists

[vincentjanv]

Since about a month we are having major issues with forwarders and mailing lists.

We have searched the forums as well as google for days.
Forwarders seem to be hit and miss, sometimes the messages go through to some receivers but it seems totally random.
we have proper spf,dkim and dmarc records and use ptr records and conduct tests via mail-tester.com to make sure we get a 10/10 score, we also monitor blacklists.
Regular emails work fine.

In searching the forum we found some posts containing a setting that blackhole certain messages to avoid backscatter, commenting this setting just makes it so that nothing works anymore.
We have also created mailboxes for the forwarders since this was recommended, no change.

When we send to a forwarder there is often nothing found in the smtp logs so it seems like the messages are just getting blocked somewhere and not even getting attempted to be sent most of the time.
Reading up on exim config settings has not been fruitful as we cannot find anything that indicates this type of random behaviour.

As this affects our +30 shared hosting servers you can imagine we get a lot of tickets for this issue and cannot seem to figure it out.
Does anyone have a clue where to look or what could fix this? I can't imagine no other hosting firm has this issue.

 

[kristian]

The MX for the domains with problems do not see an attempted delivery? If so, the sender should get a bounce back from their sending MTA.
If the MX for the domains *do* see an attempted delivery, it should be easy to track down the reason for it? No logs of this seems very odd.
Are forwards forwarding to accounts on the same domain, or different domains? If different domains, are they local to the same server, or external?

Doing a rebuild of exim/exim_confs and possibly even dovecot/confs might be worth trying, if you haven't already.

 

[floyd]

Sometimes people make the mistake of setting up email accounts AND forwarders. You should have one or the other, NOT both.