After you install Cumulative Update 2 (CU2) for Exchange Server 2013 in your on-premises environment, you notice that Outlook Web App redirection no longer works in your Exchange hybrid deployment.
For example, when a user who has an Exchange Online mailbox connects to the on-premises Exchange Server 2013 CU2 server and authenticates, the user isn't redirected to the following location as expected:
Instead, the user receives the following error message:
:-( something went wrong. A problem occurred while you were trying to use your mailbox.
To resolve this issue, install Cumulative Update 3 for Exchange 2013. For more info, see the following Microsoft Knowledge Base article:
2892464 Description of Cumulative Update 3 for Exchange Server 2013