We are shifting from Google Apps to self hosted Zimbra and facing a peculiar problem with DNS transfer.
It has been more than 24 hours, and when I type mail.mydomain.com, it still resolved to GMail interface on and off.
To be precise, on nslookup, it appears that the transfer is complete.
Then suddenly after half an hour GMail page shows up.
nslookup and ping also changes to google and my domain every half an hour.

Hence, we are losing mails, and the user interface also gets frustrating.

Please help me as soon as possible.
Our whole day has been messed up.