iam trying to install zimbra on centos platform finally i pass the errors of perl and that stuff but iam getting an error of dns :

DNS ERROR - none of the MX records for :
resolve to this host
It is suggested that the MX record resolve to this host
Re-Enter domain name? [Yes]

my host file is as follows:
127.0.0.1 localhost.localdomain localhost
91.72.208.204 imap.gmail.com mail

iam sure that something wrong on that file , the reason that my FQHN is imap.gmail.com is because i want to use zimbra mobile and i want to syncronize mails .

iam sure iam missing something please clear to me that issue about the domain and dns i searched a lot in the wikis and the forums i didnot understand the logic.

Regards and thanks in advance
hint : i can send a full documentation about installing zimbra on centos iam sure it will add help to others as me myself i didnot been able to complete that installation except from the guidance from previous zimbra installers