While migrating Office 365 mailboxes of one of our partner, I observed if they have local (on premise) Exchange 2010 in their Active Directory Environment, Outlook 2010 will not able to auto discover Office 365 mailbox. Because every time you configure a new outlook profile SCP (Active Directory Integrated Auto Discover) will pull in local Mailbox details. To get out of this situation you have to configure it manually using ExchagneGUID (for server name) + Outlook Anywhere proxy settings. But that’s too much manual work;
But we can disable SCP based autodiscover using below keys & it will able to automatically discover Office 365 mailbox.