Timo Sirainen writes:

...

I've read the web/man pages on dsync, but it's not clear to me whether dsync can be used to export (rather than import) a user's mailbox to a remote non-dovecot IMAP account.

It should be possible at some point, but currently probably won't work very well.

Ah, thanks for the clarification.

...

dsync(localuser): Error: user localuser: Initialization failed: Namespace '': Unknown mail storage driver imapc dsync(localuser): Fatal: User init failed

But this looks like you simply haven't compiled Dovecot with imapc support. See if

dovecot --build-options|grep storage

returns imapc.

Right you are.

Joseph Tam <jtam.home@gmail.com>