[NCLUG] spam help

[Matt]

Hi,

I use SpamAssasin and it works fairly well but recently I've been
receiving 40-50 messages a day from mailers, all along the lines of
"we can't deliver your email because {we think you're a jerk, this
person doesn't exist, you look like spam} and this is all because some
spammer is using my domain as a return address. I know that the mail
is not coming from my machine because I've had my machine tested and
none of the headers of these messages have anything to do with my
machine. 

Anyway, does anyone know of a way to get rid of these messages? I have
so many mail delivery messages that if there was a legitimate one I'd
never know about it.


Thanks,

Matt