Moderated Groups in Hybrid

Working with a customer who was in the middle of the hybrid migration to Exchange Online they had an issue where emails being sent to All Company were not being approved. The All Company distribution group is a moderated group and the approvers had their mailboxes On-Premise. I found the following error in the message trace:

Moderated groups leverage arbitration mailboxes to send the notification emails to the approvers. Unfortunately the approvers were not getting any notifications when the senders mailbox was in Exchange Online. In the message trace I did find a NDR for “550 5.6.0 APPROVAL.InvalidExpiry; Cannot read expiry policy.” It turns out that Exchange Online required a Retention Policy Tag for Moderation. I ran the following commands in Exchange Online:

After running these two commands messages sent to a moderated group from a cloud mailbox were able to have the notifications delivered to the approvers. This is documented in the Microsoft Docs

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