[Dovecot] Replication fails with "Remote dsync doesn't use compatible protocol"

[Rich Wales]

I can't get replication to work in Dovecot 2.2.1.  I'm getting the
following error on the machine where I'm initiating the replication:

richatwork dovecot: doveadm: Error: dsync-remote(richatwork): Error:
dsync(local): Remote dsync doesn't use compatible protocol

Both the local and remote servers are running identical versions of
Dovecot (2.2.1), so I don't understand why I would be having any sort of
"compatible protocol" problem.  Any ideas?

I posted the "dovecot -n" output for both servers in my earlier e-mail
on this issue, which I sent about 24 hours ago (and which I assume was
too long for people to be willing to read).

Rich Wales
richw at richw.org