One of the more popular deployment options for Office 365, and more specifically Exchange Online, is the Exchange Hybrid Configuration. This deployment option gives customers a way to move some of their mailboxes to Exchange Online, while keeping some on-premises. Our goal with an Exchange Hybrid configuration is to make the two physically separate environments operate as if they were one. Features such as Mail Flow, Free/Busy, MailTips, and compliance features like eDiscovery searches work seamlessly even for mailboxes in different environments.
While all of this automation is great, there are some tradeoffs. When something goes wrong with the Hybrid Configuration Wizard (HCW), what do you do? We’ve heard complaints like, “This thing is a black box!” and “Why do the errors have to be so vague?” While we are proud of the work we’ve done with the HCW, we agree that troubleshooting some of the problems can be difficult.
Read more at source: http://blogs.technet.com/b/exchange/archive/2015/02/23/automated-hybrid-troubleshooting-experience.aspx