Tutorial for setting up SSL cert for calendaring?

This is probably a simple issue…
I’m trying to set up Exchange 2007 calendaring with Asterisk. I have all the dependencies loaded, and I have the calendar configured. When I run a “calendar show calendars”, I see the one I’ve configured with a status of “free”. However, none of the events in my calendar show up. In the log, the only message I see is:

[Timestamp] WARNING[1108] res_calendar_ews.c: Untrusted SSL certificate for calendar

Digging in to the source, it appears to be trying to validate the certificate presented by the web site. Using Google, I found one link suggesting there is a cert= option for calendar.conf. This would imply I would need to get the right certificate from Exchange and mark it as “trusted”.

Is there a tutorial for this step some place? Is it so simple to do I’m just overlooking a simple step? Help would be appreciated.