Bouncing spam is a waste of time, IMHO. Spammers almost never use legitimate return addresses. By bouncing, you're just creating more junk mail for yourself as the mail servers that the spammers spoofed re-bounce an error message back to you.You can do what I do in OS X,
Set your mail to bounce them back.
I just quickly check the messages in my Junk mailbox, then select all and Command-X. Goodbye, spam!
Cheers :-> Bill