[Dovecot] Using dsync to export mail to remote IMAP account

[Joseph Tam]

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.

(The intention is to use it whenever a user leaves and wants to copy their
local mail to Google or whatever.  I currently use uw-imapd's mailutil --
it works, but it's dreadfully slow.)

As a first crack at it, I tried (on the dovecot server)

 	dsync	-o imapc_user=remoteuser
 		-o imapc_password=remotepassword
 		-o imapc_host=remote-imap-server
 		-o imapc_port=993
 		-o imapc_ssl=imaps
 		-o imapc_features=rfc822.size
 		-o imapc_list_prefix=remoteprefix
 		-o mailbox_list_index=no
 		backup -f -u localuser imapc:

I got this error:

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

Is exporting mail to a remote (non-dovecot) IMAP account even doable with dsync, or
am I completely off-track?

Joseph Tam <jtam.home at gmail.com>