[exim] Configuring PAM on Solaris 9

I can't seem to get PAM working on Solaris 9 so that I can do authenticated
SMTP over SSL/TLS authenticating with the user's unix login details.
I have the whole thing working with a fixed password as with the config
snippet below:

# LOGIN Authentication (user/password prompts) - used by OE
test_login:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = ${if and {{eq{$1}{foo}}{eq{$2}{bar}}}{yes}{no}}
server_set_id = $1

But when I try to use PAM with this snippet:

# PAM login
unix_login:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = ${if pam{$1:$2}{1}{0}}
server_set_id = $1

I get the following message:
2005-06-19 10:33:42 unix_login authenticator failed for (aardvark)
[1.2.3.4]: 535 Incorrect authentication data (set_id=foo)

I have no idea how to set up PAM correctly on Solaris (all the recipies I've
found are for Linux), but I presume is must be possible as I've seen people
mentioning that they've set it up, but I can't find any information as to
how to do it correctly. I've tried each of the following at the bottom of
/etc/pam.conf and neither works (exim is running as the user exim).

#
# Exim
#
exim    auth required           pam_unix.so.1
#exim   auth required           pam_unix_auth.so.1

I've verified that PAM was compiled into Exim:

3:foo:/etc/virtual# ldd /usr/local/bin/exim-4.43-2
        libresolv.so.2 =>        /usr/lib/libresolv.so.2
        libsocket.so.1 =>        /usr/lib/libsocket.so.1
        libnsl.so.1 =>   /usr/lib/libnsl.so.1
        libkstat.so.1 =>         /usr/lib/libkstat.so.1
        libpam.so.1 =>   /usr/lib/libpam.so.1
        libssl.so.0.9.7 =>       /usr/local/openssl/lib/libssl.so.0.9.7
        libcrypto.so.0.9.7 =>    /usr/local/openssl/lib/libcrypto.so.0.9.7
        libc.so.1 =>     /usr/lib/libc.so.1
        libdl.so.1 =>    /usr/lib/libdl.so.1
        libmp.so.2 =>    /usr/lib/libmp.so.2
        libcmd.so.1 =>   /usr/lib/libcmd.so.1
        libgcc_s.so.1 =>         /usr/local/lib/libgcc_s.so.1
        /usr/platform/SUNW,UltraAX-i2/lib/libc_psr.so.1

Please can someone help or provide me with a URL to a HOWTO for configuring
PAM correctly.

Cheers,

Tom Davidson