Trying to migrate exchange users to O365 using cutover migration. Most of mailboxes did ok, but som failed “Error  : provisioningFailedException: Failed to update one of the recipient properties.”. It would help if the error messages explained what went wrong.?After some investigation we found the solution. We had created a new global address list for this migration to only include some of the users – users in one department. Turned out some delegation or forwarding contacts was not included in this GAL.

For this deployment they where not used and could be removed.

This is how to check and verify:
Get-CalendarProcessing “Mailbox” | fl *
Clear ResourceDelegates for stalled entries.
Set-CalendarProcessing “Mailbox” -ResourceDelegates $null

When cleared: