Office 365

Office 365 users cannot see on-premises free/busy

Issue

My Customer introduced an 2013 server into the based organisation, however found that Inbound /Busy tests failed using based .

The W3SVC logs revealed the following error – the line has been shortened for clarity

POST /autodiscover/autodiscover.svc/WSSecurity & ASAutoDiscover/CrossForest/EmailDomain//15.01.0225.018 – 500 0 0 124

Cause

The server was unable to resolve mail.domain.com and autodiscover.domain.com to itself, as internal DNS had not been updated yet. This was resolved by adding static  entries for these names into the HOSTS file.

After re-testing, the issue was found to have been resolved.