External Email Delivery to O365 Group Inbox

Occasional Contributor

We have found that our O365 group inboxes are no longer receiving a copy of emails sent from external senders. If members have subscribed to the inbox then they receive a copy but not the group inbox. Does anyone else see this same result?


I don't know how long ago this changed, but I distinctly remember cleaning up emails in the group inbox from external senders and now they are just missing. The config settings has "Allow outside senders" set to on. This is true for groups that have "subscribe members" on and off. All internal emails to the group are present, just emails originating from outside are missing.


If its relevant, we are in a hybrid configuration for Exchange. All members of these groups were users created on prem Exchange and migrated to O365.  All O365 groups were created from Microsoft 365 Admin Center. 

4 Replies
What does a message trace say?

@adam deltinger We have been troubleshooting this for the past 48 hours. Message Trace shows that it goes through our Hybrid server for delivery to subscribed members even though the members have their mailboxes in O365. As we continued to test and try scenarios, message trace has been down for about 24 hours now. We do see one trace just before it went down that says pending delivery for a group that has no subscribers.


I'm mostly curious if others are able to get external emails delivered to their group inboxes?

@Stephen Daughtersgreat problem statement / description of the issue; much better than the usual "email is broken" threads. :)


Did you end up getting to the bottom of this? I've done no homework yet, has this been published as a bug or intentional behavior change?

Hi Stephen,


currently experecing the same behaviour.


If we send an external mail to xxx@domain.onmicrosoft.com


the mail is distributed to each members (if they subscribe to the flow) and into the inbox of the group.


But if we send an external mail to xxx@domain.com - members of the group get the mail but not in the inbox.


do you solved it ?


Thank you,