Search, MailTips, and Free/Busy do not work for some Office 365 users

Last Updated: January 30, 2018

ISSUE

You may be unable to search or cannot see MailTips or Free/Busy.

When viewing Free/Busy you may see the error:

"No free/busy information could be retrieved. Your server location could not be determined."

This issue occurs on build 8420.0000 and higher. A recent Outlook 2016 change affects the User-Agent that causes problems with the Exchange EWSAllowOutlook feature.

The agent changed from: User-Agent: Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.8201; Pro)

To: User-Agent: Microsoft Office/16.0 (Windows NT 10.0; MAPI 16.0.8528; Pro)

NOTE: EWSAllowOutlook looks for "Microsoft Outlook" and not "MAPI". The effect with the Exchange server configured with EWSAllowOutlook will not allow Outlook to use EWS. This will present as a 403 error back to the client. This breaks EWS and REST.

STATUS: WORKAROUND

On the Exchange server use the below cmdlet to work around the problem:

Note: You will need to use PowerShell to run these commands. For more information, see Connect to Exchange Online PowerShell.

If the setting is per user, use this command: Set-CASMailbox user -EwsAllowList @{add="*MAPI*"}

To confirm the setting was applied, run this command: get-casmailbox user | fl *ews*

If the setting is at the organizational level, use this command: Set-OrganizationConfig -EwsAllowList @{add="*MAPI*"}

To confirm the setting was applied, run this command: get-organizationconfig | fl *ews*

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See Also

Fixes or workarounds for recent issues in Outlook for Windows

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