If you plan to take a thirdparty email service like Gmail, Indiatime, Rediffmailpro or other service provider.
They will provide you with an MX record entry.
It implement its quite simple and you can do it yourself in these easy steps.
* Login to your webhosting control panel
* Mail -> Modify Mail Exchanger (MX Entry) -> [ Change an MX Entry ] -> put the MX record and click on change.
Thats it.. no other changes necessary and it starts resolving immediately.
Dharmanath