Moderated Distribution lists and Allowed senders

Question

We have some nested distribution groups in Office 365 with the top group requiring moderation and some child groups only allowing messages from allowed senders. Example:

1. Company-All group requires moderation (Bob and Jane), allows messages from all senders, and has a bunch of child groups
2. Department-Finance group is a member of Company-All, does not require moderation, but only allows certain senders (Bob, Jane, and Mary)

Ed recently sent a message to Company-All. One of the moderators (I'm not sure who) approved the email. Everyone in the company received it, including Department-Finance.

Any idea how this is possible since only Bob, Jane, and Mary are allowed to send to Department-Finance? Is it possible that because Bob or Jane approved the message, Exchange Online saw them as the sender and thus allowed it through? I checked the internet headers and the only sender is Ed.

Thanks.

Answer 1

@AlexCarlock-4833

I did the testing in my lab and get a different result which looks more logical:

Group1 :

Group2:

Then Admin sends email to group1, User C.C approve this email:

User A.A in group1 could receive this email successfully:

Then Admin receive an email which said cannot send emails to Group2:

So, if your group configuration are correct, this email will not be accepted by group2. I would suggest you double check about the configuration.

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Answer 2

I think I'm set up the same way. Interestingly, when Ed sent the message, he did get a bounceback, but still everyone received it. I can't show or test the actual DLs for privacy reasons, but here's the setup. I think it matches your test setup.