not authorized to relay messages through the Office 365 email servers

Question

We have a 3rd party app that needs to send an email using smtp but we get the error "not authorized to relay messages through the Office 365 email servers" with Status code: 550 5.7.64

This sort of points us to look at connectors, there is already one in the but we are un able to edit and there is no option to create new connectors !!.

if we try and edit the current one it says "you do not have permission to edit this information" . I have a full admin account with access to everything, also our 365 license providers who are also admins get the same problem.

Answer 1

Hi @Paul Wells ,

To fix this issue i had to do the following

Great to know that you've already thought of a solution and really appreciate it for your sharing!
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.". and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[not authorized to relay messages through the Office 365 email servers]
Issue Symptom:
We have a 3rd party app that needs to send an email using smtp but we get the error "not authorized to relay messages through the Office 365 email servers" with Status code: 550 5.7.64
This sort of points us to look at connectors, there is already one in the but we are un able to edit and there is no option to create new connectors !!.
if we try and edit the current one it says "you do not have permission to edit this information" . I have a full admin account with access to everything, also our 365 license providers who are also admins get the same problem.

The Cause:
The administrator account loss "Remote and Accepted Domains" role to has no permissions
The loss of "Remote and Accepted Domains" role for the administrator account leaves the administrator account without permissions to create connectors.
Then run this

New-ManagementRoleAssignment -Role "Remote and Accepted Domains" -SecurityGroup "Organization Management"  

You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks!

Answer 2

Hi @Paul Wells ,
I checked the connector in my environment, and it doesn't seem to have modified the UI layout.

Did you try creating the connector using PowerShell?
Please refer to the following command to create the connector to see if it works:

New-InboundConnector -Name "SMTP Relay POSH" -ConnectorType 'OnPremises' -SenderDomains * -SenderIPAddresses 10.11.12.13 -RestrictDomainsToIPAddresses $true  

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Answer 3

Hi, yes we have also tried various things in powershell and that hasn't worked either.

Answer 4

yes we created a new test account with full admin roles and that was still the same.

Answer 5

Hi @Paul Wells ,

We have tried all basic troubleshooting that we can do. In my opinion, this issue may be caused by the tenant backend. I would suggest that you need open a ticket to resolve it.
Thank you for your patient reply and understanding!
The following is how to contact M365 support in the admin portal:

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