On Wed, 10 Dec 2003 16:44:31 EST, Cesar Sosa <[log in to unmask]>  said:
> I put Ethereal on the box  using SENDMAIL and I am getting SENDMAIL: 451
> Errors messages.  Is that an indication that the addresses are invalid  or
> that SPAM software is blocking the LISTSERV list.  Thanks for your advice.

This would be a *lot* easier to diagnose if you gave us the entire

RCPT TO:  from the previous packet (or whatever the packet was).

and the *entire* text of the 451 error.

With any luck, the connection did *not* negotiate SMTP Pipeiining (which
is easily noticable because you'll see multiple RCPT TO headers in one packet).
If it did, we'll need the entire trace up to the point of the 451 so we can match
the commands and responses up....