There were intermittent Free Busy issues when doing lookups for Office 365 [O365] users.
The following shows up in the Autodiscover.log file:
INFO AutodiscoverPage - IsSecureConnection: False
IIS was running locally. Certificate is a SAN certificate for multiple domains. There is a "Require SSL"-Checkbox in IIS, which was unchecked.
The Autodiscover logs on the CMN Free Busy Server showed that failure's occurred when IsSecureConnection: False was returned by the service.
If IsSecureConnection: True was set by the service then the Free Busy look up worked just fine.
To resolve the issue,
