Ummm...maybe you have a virus on your computer that is sending spam mail out and you are getting the bounces back?
Also, be aware that some "postmaster bounces" are actually virii in disguise. I forget the virus, but it's an old one. Check Norton's site.
BTW, never have your email set to preview in your email client. Bad thing to do as it auto-installs certain virus emails.
Thinking on it, we had something happen similar to this a few years back on a client's network. What had happened was that another company had a virus on their system, and their mailer was sending literally tens of thousands of emails out. Our client got over 3000 in a few hours from them just because one of his email addresses was in their email database.
Otherwise, I haven't a clue.
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