Send copies of certain messages to other mail account

["Luís Fernando C. Talora"]

Fellows,

To find out what kind of mailing lists my users are participating, I´d 
link to send a copy of all messages sent from or to any account with 
"yahoogrupos.com.br" or "grupos.com.br" on its address, for a deeper 
analysis. Is it possible to do it with postfix and/or MailScanner? I 
thought about some "REDIRECT" rule on  the "header_checks" table, but 
I´d like the users to continue recieving the messages, while we analyze 
that. Any suggestions?

Thanks a lot!

Luis Talora