Outlook clients reconnecting to onsite Exchange during your migration to Office 365?

About once a month I get this question in my inbox…    Sometimes it also contains multiple swear words, but I’ll edit that here 🙂

“Nick.   I am in the middle of an cut-over migration to Office 365.   My onsite Microsoft Outlook 2013 client keeps connecting back to the in-house Exchange Server even though I have published the autodiscover record for the domain”.

So, the answer is simple but unfortunately it takes sifting through many Technet articles and forum posts to get to it.   Block Outlook from using the SCP lookup method to find the users mailbox….

Option 1.

Download this file and run on your machines running Outlook 2013.

Option 2.

Manually Add to HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\AutoDiscover a DWORD ExcludeScpLookup with a value of 1.

Option 3.

Create a group policy preference for the network to generate the above registry entry on your client systems.

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