sendmail SMTP Authentication small problem

[Paul Howarth]

Rodolfo J. Paiz wrote:
> You can't enable SMTP-AUTH for all incoming mail at all, AFAIK, since
> sendmail will only request AUTH for requests to *relay*. Sendmail will
> not request AUTH for mail to be delivered locally.
> 
> If you *can* require Sendmail to AUTH everything and everyone that sends
> mail to you, then you will only receive mail sent by your own users.

You could do this by using the "a" modifier in the DAEMON_OPTIONS for the MTA, 
e.g.

DAEMON_OPTIONS(`Port=smtp, Name=MTA, M=a')

However, this would, as has been mentioned, prevent general reception of mail, 
which is why it tells you not to do it in /usr/share/sendmail-cf/README:

Notice: Do NOT use the 'a' modifier on a public accessible MTA!

Paul.