Replication Error - Trying to Interate Users

HI,

My first post to this list;

I am trying to configure replication between two host, both hosts are having the same errors. Using ‘dovecot log errors’ gives the following errors;

Dec 11 18:05:12 Error: auth: Trying to iterate users, but userdbs don't support it (created 0 msecs ago, handshake 0 msecs ago) Dec 11 18:05:12 Error: replicator: User listing returned failure Dec 11 18:05:12 Error: replicator: listing users failed, can't replicate existing data

My version of Dovecot version = 2.2.36

My Configuration is attached.

Any help is greatly appreciated. Thanks