Undelivered message expanded

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Hello,I have a user who receives most mail just fine. But some senders never get a message deliverd to said user.&nbsp;Note, this is a normal user mailbox, it is NOT a group, however, the message trace is indicating the status as "expanded" and delivered to the group, and then names the "group" it's delivered to as the users normal mailbox (It's not a group)&nbsp;&nbsp;StatusThe message was sent to the following group: fakeusername123 @domain.com. Office 365 received the message and sent it to the group membersGroup: fakeusername123 @domain.com&nbsp;How do I troubleshoot that O365 is expanding these messages to a non existing group and not delivering it to the expected mailbox?

vasilmichev · Answer

Run a message trace and post the sanitized results here: https://docs.microsoft.com/en-us/office365/securitycompliance/message-trace-scc

jason gaffney · Answer

Does this help?It also appears to be flagged as spam, however the sender is allowed an sender.

vasilmichev · Answer

You should have checked the details for the second entry there, the one with the Expand DL action. And you do have a Redirect event prior to that, which you should check as well.

jason gaffney · Answer

I have seen those, and they do not provide any information.&nbsp;The redirect detail is this "Redirect message. No detail information available".&nbsp;The second message I assume you are referring to is the Expand DL "The message was sent to a distribution list (DL) That was expanded to the recipients of the DL"&nbsp;This is the problem, the so called distribution list it's expanding to is NOT a distribution list and there is no detail in the message trace.&nbsp;Like I said, the message trace is telling me it's being sent to a group that does not exist.&nbsp;See below, I have changed the actual recipient to fakeuser123@fakedomain.com, which is a normal user mailbox, however, the message is telling me it's being delivered to the the group "fakeuser123@fakedomain.com", which is not a group, it is the users mailbox. Who never recieves the message.&nbsp;&nbsp;The message was sent to the following group: fakeuser123@fakedomain.com. Office 365 received the message and sent it to the group members.Group: fakeuser123@fakedomain.com&nbsp;&nbsp;

vasilmichev · Answer

I get what you're saying, but I also see what's on that screenshot and when there is an Expand event, usually a group is involved. Check the async message trace, it might reveal some additional details. And you can always open a support case and have this properly investigated.

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