I keep getting hundreds of emails backed up in my Deferred queue. I do not have an open relay but scanning the headers of the emails, it sure looks like I do. They purport to be 'from' me and are usually phishing scams of some sort, and I've tracked them back to all sorts of other countries and obviously compromised machines. What I'm trying to determine is if they're simply forging headers and claiming to be from me, or if they really are somehow. If I don't have an open relay, is it possible they're still actually coming from my server?