Facebook has launched new Facebook email service. But this email service is not comparable with any of other mail services like Gmail or yahoo mail and on the other hand, currently it is on “Invitation” Basis.

Facebook has build a social inbox that not only filters out spam but messages it deems less important from strangers or overly chatty friends, and impersonal messages such as the phone bill. Those lower-priority messages will be tossed in a separate folder labeled "Other." Users can also tell Facebook to automatically block messages that don't come from friends. To communicate with a friend, a Facebook user would click on the friend's name rather than hunt for a phone number or an e-mail address. If that friend prefers to get text messages, that's how the message will be seen. If the friend likes e-mail, e-mail it will be. The messaging system, however, isn't e- mail. It doesn't use subject lines or "Cc" fields. Facebook says it will store every missive sent between two people for eternity, unless they choose to delete it.

So if you are really excited to get this new service you'll have to apply for a invitation here.. http://www.facebook.com/about/messages/

You will get the invitation as soon as the Facebook team reaches you.