This is often caused when the sender of an e-mail has spoofed (forged) your e-mail address to help get through any spam filters or deceive the user who may be reading the e-mail.

1. A spammer may circulate through a list of millions of e-mails and use each e-mail address as the sender of an e-mail to help deceive the spam filter into thinking e-mails are coming from multiple sources and not a single source.
   
2. A Spammer uses a server that bounces e-mails to distribute their spam by sending all spam e-mails to that server using the From: address field. Because they're invalid e-mails, that server would then bounce them back to the users who he/she wishes to spam and because the server is a legitimate server it wouldn't be blocked.
   
3. A spammer may use your domain name to help generate fake senders of e-mails. For example, [You must be registered and logged in to see this link.] , [You must be registered and logged in to see this link.], etc.
   

What can be done?
If you have your own domain name that has unlimited e-mail addresses, sometimes referred to as "catch all", limit it. Specifying what e-mail addresses are valid (e.g. [You must be registered and logged in to see this link.] is valid [You must be registered and logged in to see this link.] is not) can greatly reduce your amount of spam and bad bounces. If your ISP or web host has an online control panel (e.g. cpanel) you can adjust this setting through it. Otherwise you'd need to contact your ISP or web host to have this changed.

If you're using a generic online e-mail service (e.g. hotmail) or an e-mail address from your ISP unfortunately there really isn't anything that can be done to prevent receiving these e-mails. Our best solution would be to filter or setup rules and policies for incoming mail to automatically delete these messages if you're receiving a lot of these bounced e-mails.

Has my e-mail address been stolen or hacked?
No. As mentioned above it's likely your e-mail address is only being used by a spammer to help get around spam filters.

Do I have a virus?
Not likely. As mentioned above its more reasonable to believe that your e-mail is being used by another spammer without any knowledge if that e-mail is valid or not. If you're concerned about a virus infection though it never hurts to scan your computer. 

ISPs and users running a spam filter or mail server.
If you're running any spam filter or mail server we strongly suggest that you do not bounce back any spam e-mail, virus infected e-mail, or invalid address e-mails.

If you're running a mail server and want senders to know the address is invalid, reject the e-mail during the SMTP transmission instead of bouncing the e-mail after it's been received. This could save you, your server, and other Internet users a lot of time and headaches in the future.