I have tried again to send mail to outside domains.But it says in zimbra log as follows
Jun 19 07:31:29 pop postfix/smtp[24763]: 6D8AB802318: to=<ask2me007@gmail.com>, relay=none, delay=0.2, delays=0.14/0.05/0.01/0, dsn=4.4.1, status=deferred (connect to 59.93.43.183[59.93.43.183]: Connection refused)
Jun 19 07:31:29 pop postfix/smtp[24766]: 7BB8C802317: to=<ask2me007@gmail.com>, relay=none, delay=0.15, delays=0.09/0.04/0.01/0, dsn=4.4.1, status=deferred (connect to 59.93.43.183[59.93.43.183]: Connection refused)