This question already has an answer here:
I have two email addresses (or more!), one of which I'm using for Stack Overflow (with my current account), while I am certainly not using the other anywhere on Stack Exchange.
Recently, I've received an automated message from the Stack Exchange team like this one, on the other email address:
Recently, you answered a question on The Workplace Stack Exchange, but you haven't verified your email address yet.
Click on the following link to verify your email and set a password so that you can log in.
Set Your Password
A few days later I received a similar message saying that I answered a question on the Islam Stack Exchange.
Obviously somebody who used my email address (on purpose or by accident) for their account, is posting answers to some of the Stack Exchange sites.
What should I do in this case? How can I prevent him from using my email address for their account?