What should I do if someone unknown is using my email address? My email account was used to register on sites.

Change your pass word. Hit spam for the mails.

What should I do if someone unknown is using my email address? My email account was used to register on sites.
Whenever you go to a site (you or someone unknown to you) to sign up or register for something using an email, the comany (website) always sends an authentication email to the email account that was used. There will be a link in the confirmation email that says something to the effect of "no, i didnt not sign up for this". Click on that, and it will remove your email address from their server. If you confirmed the account, and start receiving emails from a 3rd party service that you no longer want to receive emails from, then click the "unsubscribe" link at the bottom of the email.