There are two likely causes: The first, as described by Hippy is that someone else is faking your address, and you are then getting the genuine bounces. The other is that they are viruses which are not genuine bounces at all, but made to appear so, to encourage you to open them. In either case, the fault is not with you!
I get around 600 junk mails a day (I have a number of e-mail accounts) and use the excellent MailWasher to filter the spam. Around 60% are true bounces, 30% are fake bounces, 5% are pure spam, and the rest are real e-mails!