Be careful with Outlook customizations! Use AutoDiscover!

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During a migration from Exchange 2007 to 2013, we moved several mailboxes as pilot users. Coexistence was fully configured and on my test machine everything worked fine. However, the pilot users had trouble connecting with Exchange 2013 after their mailbox was successfully moved to Exchange 2013 servers. OWA and ActiveSync worked without any hitch.

The problem was that Outlook would update its server settings, even though (internal) AutoDiscover worked perfectly. Outlook seemed to retain its settings for Exchange 2007,
which shouldn’t be the case. Due to architectural improvements in Exchange 2013, Outlook server setting isn’t a servername or CAS array FQDN anymore but a mailbox unique GUID combined with a @ + UPN suffix. Obviously this is not a server that Outlook can connect to, but as Exchange 2013 now always uses Outlook Anywhere externally and internally it that isn’t an issue. However, you can’t easily change those server settings as you would have to determine the specific GUID which can be a hassle for a servicedesk. So, Outlook really requires AutoDiscover to set server settings.

After investigation we determined that the Office 2010 deployment had customizations in place from the Administrative Installation Point, including hardcoded server settings towards the Exchange 2007 server environment. As it seems, these settings were so pervasive that a mailbox move to 2013 didn’t correctly update. Even when we forced (try, try again and when you don’t succeed use a hammer) and Outlook could connect to Exchange 2013, some features were still broken (OOF settings, for instance. Which relies on Exchange Web Services). A brand new profile seemed to mitigate all issues.

AutoDiscover was introduced with Exchange 2007 and was supported from Outlook 2007 and forward. Therefor it’s a mystery why the server settings were deliberately set in customizations. It might have been prudent during the Exchange 2003 days (which will end in about a month when mainstream support ends), but it’s unwise in combination with Exchange 2007, very unwise with Exchange 2010 (especially when you have site resiliency plans) and just plain st*pid with Exchange 2013. It’s not only there for initial setup, but also for any High Availability/failover plans you might have.

If you find the initial Outlook setup screens requiring user interaction by pressing Next and then Finish annoying, which even appear when connecting with a domain joined computer, you can let Outlook skip those by using the Office/Outlook GPO Administrative Templates specific for your version of Office. Enable the “Suppress recommended setting dialog” in the GPO. More general info here (specific for Office 2010).

TL;DR: don’t customize/script Outlook to connect to a predefined Exchange server. Be smart, let it use AutoDiscover.

Thanks to coworker SanderV for his investigation!