As BPOS tenants start to move into Office 365, official guidance states that all users should be running the Sign-In Client (SIC), in order to help the user through the transition. I’d like to spend a few minutes describing in detail how this works and WHY administrators should NOT be looking to uninstall the SIC until the proper time.
Monday Morning – After Transition
The user logins into their PC and the BPOS SIC may or may not automatically login, depends on whether this option was set. The user SHOULD login to the SIC and then either launch Outlook from the SIC or launch Outlook and use the BPOS Outlook Profile. The SIC pull down a user certificate in addition to logging the user into BPOS and this certificate is a very important process for Outlook redirection into EXO365. The BPOS EXO Availability service, which does MBX lookups, determines the BPOS user’s MBX has moved and will redirect Outlook into Office 365’s Messaging environment. The Availability requires an online client certificate in order to communicate and determine their MBX has moved into Exchange Online 365.
So all Transitioned users who use Outlook for BPOS and will continue to use Outlook for Office 365 should login to the SIC Monday Morning, which will allow Outlook to properly communicate with BPOS EXO, find their moved mailbox (MBX) and connect into Exchange Online 365. If the SIC is no longer installed or not running, the Outlook redirect process will not work and you will have to manually configure Outlook, which will work, but takes time to configure and may very well be a large burden on administrators needing to reconfigure these PCs:
Resource: How to Manually Configure Outlook for Office 365: http://blogs.rosebudtech.com/2011/08/office-365-manually-configure-outlook.html