may i suggest to use a valid certificate, one of these official ones (eg https://www.namecheap.com/security/ssl-certificates/comodo.aspx ) that is excepted by outlook? you could also try to create your own ca and make outlook aware of it.
Sent: Friday, June 24, 2016 at 10:46 PM
From: "\"Gerald Brandt\" (g...@erlphase.com)" <firstname.lastname@example.org>
Subject: [SOGo] Free/Busy and Outlook 2013
Is there a way to get free/busy info from SOGo using Outlooks free/busy
I've tried this: https://<hostname>/SOGo/dav/public/%NAME%/freebusy.ifb
but it doesn't seem to be working. I am running an invalid certifcate.