Well if the master server is working fine then how about this. Copy main.cf and master.cf from both servers into /tmp and diff the two. Obviously the server names etc should show up but you spot the other things that are different aswell.
I am still having the same issue. I did a diff to the main.cf files and the result is as below
Please suggest some solution.
# diff main.cf /opt/zimbra/postfix/conf/main.cf
< myhostname = slave.hostname.net
> myhostname = master.hostname.com
< mydestination = localhost
> mydestination = localhost master.hostname.com
< relayhost = <IP Address>
> relayhost =