Empty Mail From: command

[Denis Gasparin]

Hi,
        what is the syntax of badmailfrom to block senders that issue empty "MAIL 
FROM:" commands? I've tried "@" or empty line but didn't worked...
        I have read past in the mailing list that there is a problem with bouncing 
messages in blocking mails with empty senders... but i haven't understand 
why...
        Can anybody give me an answer?

Thank you in advance,
Denis