How to get email and password back?

Not really. You should've kept it somewhere, like a pass'd file in your computer.

 

I personally prefer KeePass. It's amazing.

The email you can get from "account settings" somewhere when signed into your gamertag.
If not, click "Forgot your password"
And if you really still can't use that, try calling Microsoft.

 

if you go to xbox.com and fill in the e-mail address you registered with they will e-mail you your account info

 

Call Microsoft, and tell them you need to recover your account. They will ask you information like:
Phone #
Address
Email...
Don't panic if you don't know these, she will give you recovery questions to answer. It will take a minute to recover all the information, but hey, its worth it.