[Exim] Pam, smtp auth, and exim-3.36

I'm trying to get smtp authentication working on a new machine, without
much luck. I've got the same situation setup on an older machine (read:
older libraries, older pam, older exim version), but the same setup is not
working as expected. Seems pam won't let the exim user authenticate user
passwords, even if its authenticating off a password file that is readable
by the exim user.

Heres the relevant lines from the exim pam file:

auth       required     pam_pwdfile.so pwdfile /etc/mail/exim.passwd
account    required     pam_unix_acct.so

Heres the relevant lines from the exim config file:

plain:
        driver = plaintext
        public_name = PLAIN
        server_condition = "${if pam{$2:$3}{1}{0}}"
        server_set_id = $2
login:
        driver = plaintext
        public_name = LOGIN
        server_prompts = "Username:: : Password::"
        server_condition = "${if pam{$1:$2}{1}{0}}"
        server_set_id = $1

Now when I run exim as non-root, I get 'Authentication service cannot
retrieve authentication info'. When I run as root, it authenticates
correctly.

On my older setup (which does work running as exim mail user, not root)
the only difference is in my pam config file:

auth       required     /lib/security/pam_pwdfile.so pwdfile /etc/exim/passwd
account    required     /lib/security/pam_pwdb.so

So the second line 'account' is different. But I couldn't find pam_pwdb.so
on newer debian installs.

Anyone know how to get pam to be mail user friendly? Any info is much
appreciated.

-Don