Thank you for the details. As per your suggestion, I have made the changes to dovecot.conf file. Still I don't see any replication is happening. Please see the dovecot.conf file.

I do not see "/etc/dovecot/conf.d/12-replication.conf" in my servers. So I had put everything  in the dovecot.conf file only. Please see the complete data in it below. The below data is in

There should be other config files in /etc/dovecot/conf.d/ - if 12-replication.conf is not there you can just create it, but putting it in dovecot.conf will work too.
(it is easier to locate a specific configuration this way as to search a long dovecot.conf)

server A. In other server (server B) Also I have the same configuration, except mail_replica line and it is pointing to the other server like, " mail_replica = remote:vmail@bal3200dev001.testorg.com ". 

I have generated/configured the ssh keys also for vmail user in both servers. Now When i manually ssh to the server, it is not asking for a password. 

That's good.

userdb {
        args = uid=vmail gid=vmail home=/z1devenv/mail/virtual/%d/%n
        driver = static
        }

The replication wiki says:

Make sure that user listing is configured for your userdb, this is required by replication to find the list of users that are periodically replicated:
doveadm user '*'

Did you try that?

I think doveadm user '*' will not work with static userdb because no users are actually configured.

You could try https://serverfault.com/questions/939418/how-do-i-configure-doveadm-a-with-passdb

passdb {
    args = scheme=sha512-crypt /etc/mail/passwd
    driver = passwd-file
}

userdb {
    default_fields = uid=vmail gid=vmail home=/var/vmail/%d/%n
    args = /etc/mail/passwd
    driver = passwd-file
}

I've never tested this as I have my users in a mysql database.

If it works you should see some output like the following from doveadm replicator:

# doveadm replicator status
Queued 'sync' requests        0                                                                                                                                                                               
Queued 'high' requests        0                                                                                                                                                                               
Queued 'low' requests         0                                                                                                                                                                               
Queued 'failed' requests      0                                                                                                                                                                               
Queued 'full resync' requests 0                                                                                                                                                                               
Waiting 'failed' requests     0                                                                                                                                                                               
Total number of known users   1234

# doveadm replicator status '*'
username          priority fast sync full sync success sync failed
list@gcore.biz    none     00:00:28  05:52:55  00:00:28     -     

                 
Best regards
Gerald