sendmail and SMTP client-side authentication

Dan Strick strick at
Tue Dec 2 00:02:13 PST 2003

(Please forgive me if you see this twice.  I think I may have
accidentally already emailed this without a subject, but I am
not sure.  Sendmail is giving me a very hard time these days.)

My ISP assigns my IP address dynamically.  For this and other
reasons I have to relay all my outgoing email through my ISP's
SMTP email relay.  I tried to enable sendmail SMTP client-side
authentication on my FreeBSD 4.9 system by adding this line to
my file:

	FEATURE(`authinfo', `text -o -k0 -v1 /etc/mail/authinfo')

and creating the file /etc/mail/authinfo with these contents:         "U:userid" "P:password"

(of course "userid" and "password" are not the real values).

When my sendmail connects to the email relay, the email relay says
(in SMTP speak):

but there is no obvious exchange of authentication information
and my ISP's email relay sometimes rejects my attempts to submit
email for relay.  This is a typical SMTP rejection message:

    553 sorry, that domain isn't allowed to be relayed thru this MTA (#5.7.1)

Sometimes my email gets through.  I don't know why.

When I send email via Netscape, Netscape does authenticate itself
to the email relay.

Note: I did do a "make" in /etc/mail after changing
the .mc file and I did restart the sendmail daemons before sending
the rejected email.  The authinfo file belongs to root:wheel and
has mode 640.  I also tried it with mode 644 just in case.  I also
tried creating the file /etc/mail/access with the same contents and
doing "makemap hash /etc/mail/access".  The file
contains the standard line:

	FEATURE(access_db, `hash -o -T<TMPF> /etc/mail/access')

Can someone who knows how this is supposed to work help me out?

Is there an SMTP authentication protocol that protects the
authentication information from network snoopers?

Dan Strick
strick at

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