Microsoft confirms Outlook bug dropping error 603: Can't configure Exchange Online mailbox

[German]Microsoft has published a new support article that addresses an error in the Outlook desktop application. Users receive error 603 "Can't configure Exchange Online mailbox" during autodiscover while configuring a connection to an Exchange Online mailbox.

The post, with a revision date of October 17, 2022, is titled Can't configure Exchange Online mailbox in Outlook Desktop and applies to Outlook for Microsoft 365 Outlook 2021 Outlook 2019 Outlook 2016. The issue is an Error 603 that occurs during the Outlook Connectivity-Test with Exchange Online.

As a result, users may not be able to configure mailboxes in Outlook for Windows. An error during the Autodiscover process prevents the process from completing. Error code 603 is reported back with the following XML schema.

<Autodiscover xmlns:xsd=http://www.w3.org/2001/XMLSchema xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xmlns=http://schemas.microsoft.com/exchange/autodiscover/responseschema/2006>
<Response>
<Error Time="11:20:40.9842288" Id="1507709422">
<ErrorCode>603</ErrorCode>
<Message>Deleted objects will not be found with a session scoped to TenantLocal or AllTenants, unless search is scoped to Deleted Objects container.</Message>
<DebugData />
</Error>
</Response>
</Autodiscover>

The root cause: Get-Mailbox  points the SharingPolicy to a deleted object (for example, default Sharing Policy DEL:12345b67-1ab0-1234-abc1-ab1c23456789). A code fix to address the issue will be made available soon, Microsoft writes. Until then, Microsoft suggests a workaround for administrators to fix the issue.

1. Connect to Exchange Online PowerShell:  Connect to Exchange Online PowerShell

2. Confirm that Get-Mailbox references the SharingPolicy to a deleted object by running the following command::

Get-Mailbox -ResultSize 10 |fl *sharingpol*

3. Restore the default SharingPolicy by running the following:

New-SharingPolicy -Name "Default Sharing Policy" -Domains '*:CalendarSharingFreeBusySimple', 'Anonymous:CalendarSharingFreeBusyReviewer' -Enabled:$true -Default:$true

Confirm that Get-Mailbox no longer references the SharingPolicy to a deleted object:

Get-Mailbox -ResultSize 10 |fl *sharingpol*

Configure the mailbox again in Outlook and it should work again. (via)