Do we sync system arbitration mailboxes in hybrid

[Abdul Farooque]

Team,

I have a question..do we sync system mailboxes arbitration in hybrid...I'm asking bcz migrated users can not find approval system mailbox and get ndr as recipient can't find..it seems like exo looks for the object online n since it's not there, it throws ndr...

Please response how we can fix...do I need to enable sync for these system mailboxes?

[#2]

No, they are excluded by the default sync rules. A mailbox moved to O365 will use the corresponding system mailbox(es) in Exchange Online. In Hybrid scenarios, there are certain configuration steps you need to perform, check out this recent article: https://techcommunity.microsoft.com/t5/exchange-team-blog/demystifying-moderation/ba-p/2566197

[#3]

Thank you. So how to fix issue when moderation is enabled in hybrid and approval goes to onPremises Approval Mailbox..EXO can not route cz the object Mailuser is not there... I'm getting ndrs for users migrated online ...
When a migrated user sends to this approval mailbox..there is an ndr