This will only work if the Account has a Parental Control set up. (most sold accounts do to protect the seller from being scammed)
First what you need to do is log into the Account Management for the Account you need the email for, it should look like this now:
Now click where it says Parental Controls:
On the second step they might ask you for the SQ/A if the Parental Controls have never been set up before, in this case the method I provide will not work
Sorry!
Most people selling accounts turn on the Parental Controls to "All Red" meaning you can't play on the Account.
Here is what it looks like:
Ok, now find the Parental Control Password box and click "Change your password?"
And (hopefully) if the Parental Controls was set up with the Account email, then you have just found your victims email!
.gif "(6)")
Obviously this method isn't foolproof, but if you're stuck and have no other method of getting the email you might as well try this.
Finding the email on an Account 
is appreciated. If you help me, I'll do the same for you.
