yes you are right. I became a bit desperate yesterday - after hours of trying to fix the problem.
OK, we need to receive Mails with about 40MB of size. This is an automatic and repeating task, so there is no way to split the attachement.
For that mails I get the entry in zimbra.log:
First I set the MTA Mail max size in the Admin console. But this just seems to relate to the size of mails to send.
fetchmail: SMTP-Fehler: 552 5.3.4 Message size exceeds fixed limit
Following the wiki article Configuring maxmessagesize - Zimbra :: Wiki doesn't work for me.
So far involved variables:
zimbraFileUploadMaxSize: This is just to upload files to Zimbra? I should not need to change this?
zimbraMtaMaxMessageSize: This is to define the the max size to send mails? Also to receive? Otherwise I would prefer to keep this small.
zmprov gcf zimbraFileUploadMaxSize
zimbraMailContentMaxSize: What is this exactly for?
zmprov gcf zimbraMtaMaxMessageSize
postconf message_size_limit: it seems this needs to be adjusted - but how?
zmprov gacf zimbraMailContentMaxSize
What is the right way to restart what service to have the changed values to take effect. For now I just restarted the whole thing to be sure.
message_size_limit = 25600000
I hope this is all the information you need?