[Mimedefang] Agressive spammers

[dimon at intellinetinc.com]

Hello!

Recently, after I implemented tight spam filtering, spammers started behave 
very agressive: they're using my domain names (with nonexistent users) and 
sometimes even existent users. So now I'm getting a lot of bounce messages from 
legitimate email servers (vacation replies, nonexistent users, spam filtering 
messages, etc.).
And users are complaining that they're receiving those messages.
Is there anything I can do about that? Does it worth any efforts at all? Does 
anyone experiencing the same problem?

Best regards,
Dmitry