Hydrid DL and 5.4.12 error

sim3vi 166 Reputation points

In a hybrid exchange environment I deploy a DL on exchange on line. The members of this dl are all on cloud.
If I send an email to dl from inside the organization it works.
If I send an email to dl from outside the organization after some time I recive a messager form postamaster of my organization with error 5.4.12.
The dl deployed onprem works.

Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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  1. KyleXu-MSFT 25,616 Reputation points


    To narrow down this one, I would confirm some information with you:

    Whether this phenomenon occurs on all Exchange online distribution group? If this phenomenon only occurs on a specific distribution group. I would suggest you try to create a new one.

    Whether you modify the default hybrid connector before? If you modify it before, I would suggest you try to rerun HCW to create a new one.

    Which email address that you used for this distribution group? I would suggest you try to use the Exchange online default domain for this group then check whether the phenomenon is gone.

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  1. Michel de Rooij 1,521 Reputation points Microsoft MVP

    For the DL to accept messages from outside the organization, you need to remove the requirement that senders need to be authenticated, e.g.
    Set-DistributionGroup -Identity <DG ID> -RequireSenderAuthenticationEnabled $False

    Note that this may open up the DG for spammers from outside.