[Exim] Enabling SMTP AUTH over SSL only (redux)

To answer the questions:

I am running Solaris 9 SPARC with Exim 4.22 /w PAM support
compiled in (verified with ldd).

I only want to allow AUTH over encrypted connections; I'm
using a self-signed certificate.

"Never attribute to malice that which can be explained by stupidity."
    - Author Unknown