Hello,
I look after a server that was bouncing back emails sent to it with messages greater than 15M in size. I also run a server here for my own use, and it was fine. The bounces all stated that mail.mydomain.co.uk had rejected the message because the message was too big. For example:
The original message was received at Wed, 5 May 2021 13:47:11 +0100 (BST)
from mail.otherdomain.com [xx.xx.xx.xx]
----- The following addresses had permanent fatal errors -----
<user@mydomain.co.uk>
(reason: 552 Message too big!)
I checked out the wiki entry here:
https://wiki.koozali.org/Email#Set_max_email_sizeand also this forum post:
https://forums.contribs.org/index.php?topic=54070.0;topicseenThere were two differences in settings. The first was in clamd MemLimit, which was 15M on my server, and 18M on the problem server. This was because I'd had the error reported in the forum post a while back.
The second was in the qmail MaxMessageSize, which was 45000000 on my server, but only 15000000 on the problem server. After changing this to 45000000 on the problem server it appears to have fixed things.
I'll not raise a bug as I don't know if I've changed my settings at some time in the past and just forgotten.