Message Moderaton Approval Loop in Hybrid Scenario



I am currently troubleshooting an issue for my client in regards to message moderation. The current set up is an Exchange 2013 Hybrid solution and they have a mail flow rule set up for sending all mails containing a zip file to a mailbox for approval. This was working fine until the mailbox was migrated to Exchange Online. Now the e-mails sent for approval are failing with the following error Reason: [{LED=550 5.2.0 Resolver.MT.ModerationLoop; Loop in approval process};{MSG=};{FQDN=};{IP=};{LRT=}].

If I recreate the mail flow rule then I get the same issue and if I turn off moderation, then the mail gets delivered without the moderation option.

I've run out of ideas on how to resolve this issue, so I am turning to my peers in the community for help please.

Rgds Lee

2 Replies
Which mailbox did you move? The sender or the target that the approval goes to?

Would suspect you need a rule in both on prem and the cloud to deal with this, and if not, ensure that your hybrid connectors are doing auth properly - that is, emails are authenticated between onprem and your tenant

Hi Brian,


Thanks for the reply, The mailbox was the target one for approval. There were rules on both on-prem and exchange online.


I fixed the issue by enabling TNEF on the remote domains and turning off Moderation on the mailbox. I added the address to the outbound to O365 send connector and the decision buttons appeared. I then had to create contacts for the on-prem arbitration mailboxes as the accepted domains are authoritative and they weren't synched by AAD Connect. The approval now works although it send two messages.