hank you very much for your reply.
Now coming to my problem. When installing zimbra i got this error.
Then i tried to accept changing domain name.
DNS ERROR resolving MX for mail.ardhi.go.tz
It is suggested that the domain name have an MX record configured in DNS
Change domain name? [Yes]
Create domain: [mail.ardhi.go.tz] ardhi.go.tz
MX: mail.ardhi.go.tz (172.16.16.2)
Then installation completed without any error.
Now when i try to send mail to outside world i.e gmail i see this error in the mail queue (differed)
What could be the problem?
Host or domain name not found. name service error for name=gmail.com type=mx: host not found, try again