On Mon, 8 Jan 2001, John Maier wrote:

> MAIL FROM:<>
> 
> and the sendmail thinks the mail is from postmaster.
> 
> So how do I create a rule to tell sendmail to disallow blank 'from' emails?

You probably don't want to reject mail because of a null or blank envelope
from address.

RFC 1123 says an "empty reverse path MUST be supported" and:
 If there is a delivery failure after acceptance of a message,
 the receiver-SMTP MUST formulate and mail a notification 
 message.  This notification MUST be sent using a null ("<>") 
 reverse path in the envelope ...

Maybe you can use some other rules or ideas to block these spammers.

   Jeremy C. Reed
   http://www.reedmedia.net/