Cloaked Emails :

A spammer sometimes copies a legitimate email address to illegally bulk email.
If you received an auto response for an email you did not send, then this is what has probably happened. This is called a "cloaked" email.

Another way your email address could crop up is from a virus. A compromised computer may have picked up you email address and is using as the sender address. This happens when viral messages are being transmitted.

It is a common practice and eventually these email notifications will fade away as the spammer moves to a new name. You are not affected because your IP address and the spammers are quite different (usually the spammers IP address is hidden).

Disregard these notifications.