Ok, now that we’ve talked about how to prepare for the move, lets go ahead and see what you should take care of during the move.
Performing the move
Before the move
If you have modified the TTL values for your DNS records correctly, the number of problems you will face because of a server move, will be greatly reduced. However there is more thing you could do before you start the move to try and avoid more problems. That is to shutdown the mail server on your old server. You should understand that shutting down the mail server does not necessarily mean mails to the accounts on your server will fail and will never be received. Instead, once the mail server trying to send the mail sees that the mail server is down, it will keep the message in its queue and will attempt to deliver it later. By then the TTL would have passed and when it tries to send the mail again, it will be delivered to the new server.