If you’ve attempted an install and migration to Small Business Server 2011 only to receive the dreaded yellow exclamation point, indicating something happened during the process, you’re probably thinking that you’re going to have to go back and do the process over again. The good news here is you may not have to. If you take a look at the migration issues and it indicates that Microsoft Exchange 2010 didn’t install, then you can probably still salvage the situation. You’ll want to go ahead and generate the SBS Logs for the install process and scour through the Exchange install log looking for the reason it failed. Once you find the reason for the failure, you’ll need to find a fix for the problem.
If for example you find out that the install of Exchange 2010 failed because the Discovery Mailbox already exists, then all you need to do is delete the user from Active Directory Users and Computers, then you can proceed.
Once you’ve fixed the reason Exchange couldn’t install completely, you’ll need to manually kick off the install process. The installer for Exchange 2010 is located on the SBS 2011 Repair DVD, under the CMPNENTS\EXCHANGE14_SP1 folder. If the problem is fixed, then the setup should finish installing the missing Exchange roles.
Now there’s a few more steps that must be completed to finish the SBS 2011 install process and activate Exchange. The steps are outlined in this Microsoft KB: http://support.microsoft.com/kb/2527626
After you’ve ran the shell script to finish the SBS setup process and the hotfix to activate Exchange, you can reboot. If all has gone well you should be greeted with the expected green checkmark of success. At this point you can continue your migration process.