so - after working on this for a few hours, this has become basically an entry for posterity, in the hope that zextras lasts long enough to make this a searchable resource. I'll also post back here with the results of my flailing. I still want a decent reference, but I'm not holding my breath.
Here is the problem description, in brief.
I am migrating from zimbra FOSS 8.8.15 to carbonio CE. I appear to have hit some kind of connection limit on the new server that I long ago fixed on the zimbra server (although that is a conclusion drawn from the intensive searching I have been doing. I have no notes of the changes, but the fixes are changes to the zimbra defaults). Specifically, we have approx 13 IMAP clients connecting to the same account on either server. When we get to attempting to connect the 12th and 13th clients to the carbonio server, Betterbird (the IMAP client) takes about 90 seconds to timeout and report "unable to connect to .... If the problem persists you may have exceeded the maximum number of connections to this server" (I see no way to include a screenshot, except as a link, which will be useless in very short order).
Is there a command-line reference for the carbonio prov commands and options? The 'carbonio help prov' command gives less-than-useful hints for this particular situation.
In particular, is there a provisioning command for carbonio CE for thie ZimbraImapNumThreads and zimbraImapMaxConnections? This is what I (must have) used for zimbra FOSS 8.8.15 ('cause the defaults recorded in various search hits from years ago for zimbra are both 200), since the current setting for both on the zimbra server is 500.
zmprov ms `zmhostname` zimbraImapNumThreads 500 zmprov ms `zmhostname` zimbraImapMaxConnections 500
This command, after a long wrestling match with claude and gemini, to get zextras to give up its secrets gives me a clue...
carbonio prov gs $(zmhostname) | grep -i imap zimbraImapMaxConnections: 200 zimbraImapNumThreads: 200 <much output elided>
The attributes exist! Now, how the bleep do I change them?
zextras@mail:~$ carbonio prov ms $(zmhostname) zimbraImapMaxConnections 500 zextras@mail:~$ carbonio prov ms $(zmhostname) zimbraImapNumThreads 500 carbonio prov gs $(zmhostname) | grep -i zimbraImap zimbraImapMaxConnections: 500 zimbraImapNumThreads: 500
now all I need to do is wait for the bulk email migration to complete so I can restart and see if it truly does have an effect