Thank you Till for responding.
I built a new master server with version 220.127.116.11 and then moved an existing slave to new master doing 18.104.22.168 on the slave. The slave is running postfix and dovecot only; now the new master is not propagating changes to the slave.
The slave server is showing in the new master except that the changes made on the new master do not reflect on the slave server.
I appreciate any help I can get to resolve this problem.