Microsoft is working on a fix for a known issue that might prevent customers from configuring Exchange Online mailboxes in Outlook for Windows.
These configuration problems are due to Autodiscover flow errors with 603 codes after the configuration process breaks during the Outlook Connectivity test.
“Deleted objects will not be found with a session scoped to TenantLocal or AllTenants, unless search is scoped to Deleted Objects container,” the error messages read.
“Get-Mailbox will point the SharingPolicy to a deleted object (eg. Default Sharing Policy DEL:12345b67-1ab0-1234-abc1-ab1c23456789),” Microsoft explains.
The known issue affects several Outlook desktop clients, with the complete list including Outlook for Microsoft 365, Outlook 2021, Outlook 2019, and Outlook 2016.
Workaround available for admins
Microsoft added that while the root cause behind these configuration problems has already been identified as a service issue, a code fix that addresses it will be deployed soon.
Meanwhile, IT administrators can manually fix it using the following steps:
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Connect to Exchange Online PowerShell: Connect to Exchange Online PowerShell
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Confirm that Get-Mailbox is pointing the SharingPolicy to a deleted object by running: Get-Mailbox -ResultSize 10 |fl *sharingpol*
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Restore the Default SharingPolicy by running:
New-SharingPolicy -Name “Default Sharing Policy” -Domains ‘*:CalendarSharingFreeBusySimple’, ‘Anonymous:CalendarSharingFreeBusyReviewer’ -Enabled:$true -Default:$true
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Confirm that Get-Mailbox is not pointing the SharingPolicy to a deleted object anymore: Get-Mailbox -ResultSize 10 |fl *sharingpol*
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Configure the mailbox in Outlook should work again.
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 it’s launched.
Redmond also recently fixed a bug that crashed the Outlook email client when reading emails containing tables such as Uber receipt emails.
Source: www.bleepingcomputer.com