Binding AMS to loopback only (single IP) – Help

So I have Exim routing mail (nicely, thanks for the help), virtual hosts working, and AMS picking up the mail on via SMTP/627. I now want to use stunnel to encrypt the traffic. To do so, I would like AMS to stop listening on the IMAPS port (since it doesn't work right anyway), or at least restrict it to the loopback (127.0.0.1) port. Then I could stunnel from the internal and external IPs into the unencrypted ports. Unfortunately, AMS grabs the ports, so stunnel fails to bind. Please help. Alex