Just in case anyone comes across this thread looking for another answer here's some info...
1. If you're using 3rd party SSL you have to have a cert that covers autodiscover.yourdomain.com, hostname.yourdomain.com and yourdomain.com
example - autodiscover.zentyal.com, mail.zentyal.com and Zentyal.com
2. If you use the self signed SSL you HAVE to install your Root CA on anything to use Autodiscover, download it from the admin panel under Mail>Openchange - there's a button to download it there. Install that cert under the Trusted Root Authorities (or something really like that), don't do the auto install it junk that doesn't work)..
3. When using 3rd party DNS you have to create the entry for autodiscover.yourdomain.com and point it to the exact same IP as hostname.yourdomain.com - yes that is kind of dumb but it's really crazy smart in getting everything to line up properly and allowing Outlook to Autodiscover things...