Docs for http://www.qmail.org/qmail-remote_authenticated_smtp.patch
a patch to convince qmail-remote to use Authenticated SMTP when
talking to certain hosts.

This version of the patch has been modified by Robert Sanders so that
base64 encoding of usernames and passwords is done automatically by
qmail-remote.

After applying the patch, the username password go into
/var/qmail/control/smtproutes like so:

domain:relay username password

The domain:relay part is identical to a normal smtproutes entry (see
the qmail-remote man page). For sites that require authentication, you
simply add two space separated fields to the line, where the first
field is the username, the second is the password. For example:

inside.af.mil:firewall.af.mil:26 johndoe secret

would send mail for inside.af.mil to firewall.af.mil, port 26 using
username 'johndoe' and password 'secret'

Since smtproutes will contain plain text usernames and passwords
you might want to make the file owned by qmailr and set its permissions
to 0600. Of course, the entries are going to go over the wire in the clear
anyway as part of the SMTP transaction.

Good luck.

j.