Microsoft is working on a fix in Outlook for a known issue that may prevent customers from configuring Exchange Online mailboxes on Windows.
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These configuration issues are caused by Auto Discover flow errors with 603 codes , after the configuration process is interrupted during the Outlook connectivity test.
The known issue affects several Outlook clients, with the full list including Outlook for Microsoft 365, Outlook 2021, Outlook 2019, and Outlook 2016.
Microsoft added that while the root cause behind these configuration issues has already been identified as a service issue, a code fix that addresses it will be deployed soon.
Meanwhile, IT administrators can fix it manually using the following steps:
Connect to Exchange Online PowerShell
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Verify that Get-Mailbox shows the sharing policy for a deleted object by running: Get-Mailbox -ResultSize 10 |fl *sharingpol*
Restore the default sharing policy by running:
New-SharingPolicy -Name “Default Sharing Policy” -Domains '*:CalendarSharingFreeBusySimple', 'Anonymous:CalendarSharingFreeBusyReviewer' -Enabled:$true -Default:$true
Verify that Get-Mailbox no longer shows the Sharing Policy for a deleted object: Get-Mailbox -ResultSize 10 |fl *sharingpol*
Mailbox configuration in Outlook should be working again after the steps above .
See also: How to block a domain in Microsoft Outlook
Two weeks ago, Microsoft began rolling out a fix for another issue known since August that causes Outlook for Microsoft 365 to freeze and crash after launching.
The company also recently fixed a bug that crashed the Outlook email client when reading emails that contained tables, such as Uber receipt emails .
