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Exchange 2016/2019 Troubleshooting: Flighting is not enabled for domain...oauth_not_available

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Error description

"Flighting is not enabled for domain user@domain.com...oauth_not_available".

Scenarios

There are two scenarios where this can happen that I have encountered:

  • Hybrid Exchange (AD Connect - Azure)
  • No Hybrid

Symptoms

On a certain day, users open Outlook and the splash screen disappears immediately after opening and you greeted with an error, "Outlook cannot open....". You try safe mode and the same thing.

Troubleshooting

I generally use Fiddler because you can see where traffic is going and the errors. Right, with fiddler running, you launch Outlook again and it crashes as it previously did but you can see an example of the error you will pick up in Fiddler:

https://www.collaborationpro.com/wp-content/uploads/2020/12/image-6-1024x353.png

Okay, so you see the error. Here are the possibilities of why it's not working:

  • You enabled OAuth on all your virtual directories on Exchange but didn't enable it under OrganizationConfig (command is Get-OrganizationConfig | fl *auth*) and it is set to False.
  • The second possibility is that with AD Connect, you only sync selected folders and a new user is placed in the default OU (Users) and has not synced to Office 365. The user can access OWA and ActiveSync but not Outlook.
  • If the FE server is pointing to Office 365, you need to enable OAuth on your Tenant using the same command as listed above.

Solution

So you either need to enable OAuth in Exchange on-premise or move the user to the right OU and wait for the Sync in AD Connect. Once all has synced, Outlook should open without an issue.