As customers move their organization into the Cloud or choose to coexist, there is a need to ensure that some of the basic functionalities users have grown accustomed to, continue to work. While some of you will move all of the users in a cutover fashion which reduces complexity, others will choose a more gradual approach. This troubleshooter is for administrators that have chosen the hybrid approach.
Are you seeing the hash marks in your hybrid Exchange environment as depicted below and want to get rid of them? Then this troubleshooter is for you.
The reason we focused on a troubleshooter for Free Busy is because it is the most commonly used “feature set” in a hybrid deployment. If you were to resolve issues with Free Busy lookups, many of the other potential issues you have with your hybrid deployment would be resolved as well.
Check it out Source.