Cannot email Office365 Groups without enabling external senders

Question

We have recently migrated our users to Office 365, and we've had a growing interest in the new Office 365 groups not only in IT, but also among our users.

One issue that keeps cropping up though is the email function. Unless the setting to "Allow people outside the organization to email this group" is enabled, no one can send an email to the group. It doesn't matter if the group's domain is "domain.onmicrosoft.com" or "domain.edu."

One receives the NDR: ****

The group only accepts messages from people in its organization or on its allowed senders list, and your email address isn't on the list.

Status code: 550 5.7.133

This error occurs when the distribution group, security group, or Office 365 group is configured to accept messages only from authenticated senders (senders in the same organization or those added to the group's allowed senders list).

To fix the issue, the recipient's email admin or the group owner must add the sender's email address to the group's allowed senders list or change the group's delivery management setting to accept messages from senders inside and outside of the organization.

Usually this issue can only be fixed by the recipient's email admin or the group owner.

For more information and steps to fix this error, see Fix email delivery issues for error code 5.7.133 in Office 365.

Error Details

Reported error:    550 5.7.133 RESOLVER.RST.SenderNotAuthenticatedForGroup; authentication required; Delivery restriction check failed because the sender was not authenticated when sending to this group

DSN generated by:    CY1PR07MB2555.namprd07.prod.outlook.com

The groups default to the onmicrosoft address, but all of our users have that as a proxy address anyway. The DNS is configured correctly as well.

The only option I've read and the only one that seems to work is enabling the internal and external senders setting, but I would think that people within the group should be allowed to send emails to the group regardless of that setting.  Is this by design, and if so why? If it's required, then the language really needs to be changed to reflect that its real purpose is to allow email.

Answer 1

Microsoft support identified the problem finding that the attribute OpenDomainRoutingEnabledwas set to $true.

They set it back to $fals e and the problem was fixed.

A couple of points on this attribute setting:

1. Only the backend engineering team can adjust the setting. So a ticket with Mircosoft is required.
2. This setting would/could change during a migration from 2010 to 2013 (or as likely in our case, in going from 2010 to Office 365 using a 2013 server for the migration).

Answer 2

OK, nevermind about the new conversation appearing in the OWA. It shows up when you first create it, but you cannot reply to it, and when you click the "New Activity" button that appears, the conversation disappears.

Answer 3

Hello, Robert. Thank you for the reply. I've submitted the requested information in the PM. 

I did not think it was supposed to be this way, but I was trying to cover various possibilities. 

2. The issue persists for anyone who tries to email the group, not just the owner. 
3. It appears to be an issue with every Office 365 group. I've created multiple test groups, and as the faculty have been starting up classes they've been experimenting as well. 

An additional wrinkle that may help (or make it more confusing), If I go into the group on OWA, and use the group view to create a new conversation, then the conversation will show up in the list, but I will get an NDR as well.

Answer 4

Hi Justin,

No, it is not by-design. Internal users can send emails to the Office 365 groups without the option “Let people outside the organization to email this group” selected.

To look into the issue, can you please confirm the following information?

1. Please send us the complete NDR (non-delivery report) for analysis.
2. If you use other internal users account to send to the group, does the issue persist?
3. Do you have the problem for all the groups or just some specific ones? I suggest you create some new test groups to test the issue.

To protect the privacy, I have sent you a private message to collect the information.

Regards,

Robert

Answer 5

P.S. the link in the error message about fixing email delivery issues pertains to settings only available in Distribution groups, not Office 365 groups.