FishNose, in this case it doesn't matter what kind of protection you have in your end. The infected computer contained your e-mail address somewhere (e.g. Outlook address book) and used it as a "Received from" address. Your computer was not involved in any way, shape or form. The same thing happened to me at work recently. Our IT-department called me one morning and informed me that huge amounts of viruses had been sent to other employees with me as sender address. When they looked into it, it was obvious that all the mails was sent at a time when my laptop was disconnected from the network, shut off and safely resting in a bag in the trunk of my car... An obvious case of a virus in another PC spoofing sender addresses!