PostFix + saslauthd + auth against shadow = frustration

[aluminumpork]

Okay, while I'm not new to Debian, I still consider myself fairly noobish. So, with that said, I need to setup up an SMTP Relay server that is NOT open. I've successfully installed and setup PostFix and am able to send mail through it.

However, I must enable some form of authentication on the server.

It seems the best way to do this is with saslauthd. I have install this, as well as a number of other packages as per many tutorials I've followed. saslauthd runs as well with no errors, as does PostFix. I have the following lines in the main.cf for PostFix:

smtpd_sasl_auth_enable=yes
smtpd_sasl_local_domain=zmcsmtp.servehttp.com
smtpd_recipient_restrictions=permit_mynetwork,perm it_sasl_authenticated,reject_$
smtpd_ssl_security_options = noanonymous

and...

smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s

I also have a smtpd.conf file in /etc/postfix/sasl/ with the lines:

saslauthd_path: /usr/sbin/saslauthd
pwcheck_method: saslauthd
mech_list: plain login

Then I have in the /etc/default/saslauthd file:

START=YES
MECHANISMS=shadow

among the other defaults.

Authentication seems to be working. When I send an email through the SMTP server, as it pops up the authentication box asking for username and password.

Am I correct to assume that since I have the mechanisms set to "shadow" and smtpd is set to saslauthd that it should pull the usernames and passwords directly from /etc/shadow? I have added a specific "smtpuser" account to Debian, which shows up in shadow, but I cannot authenticate using this. I've tried all of the other accounts there are, but nothing authenticates. Do I have to make the user part of a special group? What do I have to do get saslauthd to authenticate against shadow properly?

Thanks for any tips.

[aluminumpork]

Nobody has any ideas? I still haven't had any luck.