please help .. we are under fire !

[Petr Zeman]

Hello,

we using MailScanner+Sendmail+SpamAssassin+Clamav as an e-mail gateway 
for aprox. 100 local users. Normally we have 3 000 e-mails daily - 2500 
is spam 500 is usable. From tommorow we are under fire :-). Anybody 
nasty use our domain name (juli.cz) to send thousands spam e-mails. From 
yesterday we obtained over 100 000 non-delivery reports to fake address 
"tli at juli.cz" and her variants.

What can i do now? I only set "To: *tli at juli.cz yes" to 
spam.blacklist.rules. Is much better now, but this is not solution.

I will be appreciative, for some ideas.

Thanks

Petr Zeman
JULI Motorenwerk, s.r.o.
organizace a informatika
zeman at juli.cz