What is the place that I have to check if an e-mail is genuine or not?

Answer 1

http://www.artsci.wustl.edu/ASCC/documentation/spam/spam.html

Answer 2

You really can only check to see if the domain is real or not. The actual email addressee is checked by the domain's mail server and that information is not in the public domain.

One way is to send a test message from one of your free email accounts to see if it bounces. If not, then the email address is valid. That does not mean that the person that sent you the email is actually the person the return address is for! Email headers that contain the return address are easy to fake so if you are getting spam, the return address is probably not the actual sender.