One of these days I used imapsync to migrate the content from a Domino mailbox to a target in a "Mailcow" server.
I used the imapsync that is integrated into Mailcow and can be configured and scheduled through the Mailcow UI.
For verification I also "git pull"ed the current normal imapsync, did a "make install" and tested with this version.

The problem is that imapsync seems to totally and silently ignore (not even see) the "Sent" folder of the Domino mailbox and so this content is missed. I used the --domino1 option and --automap.

I worked around the problem by creating a new folder in the domino mailbox and added all messages from "Sent" to this folder as well (by using the Notes client) and then repeating the synchronization. This then worked fine (it synchronized this additional folder and its content).