[Exim] Enabling SMTP AUTH over SSL only

I have the following config directives in my exim.conf, but I can't
get this functionality to work (or tell if it is working). Any
assistance or guidance would be most appreciated; I know I'm missing
something I just have no idea what.

=== Start ===

tls_advertise_hosts=*
tls_certificate=/local/etc/exim/certs/<site.FQDN>.crt
tls_privatekey=/local/etc/exim/certs/<site.FQDN>.key

# AUTH - only allow auth on encrypted connections
auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}

begin authenticators

login:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = ${if pam{$1:$2}{yes}{no}}
server_set_id = $1
# server_condition = ${if pam{$1:${sg{$2}{:}{::}}}{yes}{no}}

plain:
driver = plaintext
public_name = PLAIN
server_prompts = :
server_condition = ${if pam{$2:$3}{yes}{no}}
server_set_id = $1
# server_condition = ${if pam{$2:$sg{$3}{:}{::}}}{yes}{no}}

=== End ===

NOTE: The auth_advertise_hosts was taken directly from the
Exim FAQ.

Thanks in advance!