DELIVERY HAS FAILED TO THESE RECIPIENTS OR GROUPS ERROR MESSAGE

Question

DELIVERY HAS FAILED TO THESE RECIPIENTS OR GROUPS ERROR MESSAGE

Stephen Hobbs 20

NEED HELP? HAVE TROUBLE SENDING OUT EMAILS TO OUT OF NETWORK EMAILS

Your message couldn't be delivered. Despite repeated attempts to contact the recipient's email system it didn't respond.

Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their email system isn't accepting connection requests from your email system. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.

Diagnostic information for administrators:

Generating server: REMOVE PIIprod.outlook.com Total retry attempts: 4

REMOVE PII@yahoo.com Remote server returned '550 5.4.300 Message expired -> 451 domain not found (not relaying for 40.107.208.142)'

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Answer 1

Jess-Q 12,795 Microsoft External Staff Moderator

Hi @Stephen Hobbs

Thank you for posting your question in the Microsoft Q&A forum.

Regarding your issue, may I kindly ask a few questions to help understand your issue better:

Is your account a personal account (e.g., Gmail, Hotmail) or a work/school account (typically associated with a domain name like your company or school)?
Is this happening with just this recipient or with multiple out-of-network external addresses?
Have you been able to send emails to this address successfully in the past?
Are you using any custom connectors or mail flow rules that might affect external delivery?

Hope to hear back from you soon.

The initial response may not fully address your needs, but it will help me better understand your situation. Once I get the information, I will try my best to find the next steps.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Stephen Hobbs 20 Reputation points

2025-10-07T19:05:05.9666667+00:00

IT IS A COMPANY EMAIL AND IT HAPPENS WITH ALL OUT-OF-NETWORK EXTERNAL ADDRESSES.

I HAVE NOT BEEN ABLE TO SEND ANY EMAILS SINCE I STARTED USING THIS ACCOUNT.

NOT USING ANY CUSTOM CONNECTORS OR MAIL FLOW RULES
Jess-Q 12,795 Reputation points Microsoft External Staff Moderator

2025-10-08T13:51:21.3566667+00:00

Hi @Stephen Hobbs,

Thank you for the response.

If you're using your work email, I recommend reaching out to your IT Administrator to perform a message trace in the Exchange Admin Center. This can help determine whether your email was sent but rejected by the recipient's server. Additionally, ask them to check the accepted domains list to ensure that the external email addresses you're trying to reach are properly configured.

It’s also a good idea to check with other users in your organization to see if they’re experiencing the same issue. If they are, it might be due to a policy set by your organization.

Lastly, confirm with your recipient whether they’re using a personal email address, as that could also affect delivery.

Hopefully it will help with your issue.
Jess-Q 12,795 Reputation points Microsoft External Staff Moderator

2025-10-10T14:20:22.0266667+00:00

Hi @Stephen Hobbs,

It has been a while and I am writing to see how things are going with this issue. Have you had a chance to check the replies provided? Any update would be appreciated.
Jess-Q 12,795 Reputation points Microsoft External Staff Moderator

2025-10-14T14:35:59.94+00:00

Hi @Stephen Hobbs,

This is my second follow-up to check whether your issue has been resolved. I truly want to ensure your experience is as smooth as possible. If your problem is still ongoing or if you have faced any new difficulties, please share more details about the current steps you are stuck on. I am here and happy to provide further help whenever you need it.

While waiting for your response, I will continue tracking other customer questions on the forum to ensure everyone receives timely support. If you have additional questions, please feel free to tag my name in your reply so I can assist you promptly and more personally.

Looking forward to hearing from you soon.
Stephen Hobbs 20 Reputation points

2025-10-21T14:03:54.8766667+00:00

HELLO AGAIN, JUST SEEMS LIKE MY EMAIL IS THE ONLY ONE NOT ABLE TO SEND OUT GOING EMAILS. NOT REALLY SURE WHATS HAPPENING. I TALKED TO THE IT GUY AND HE WAS SAYING THAT COULD IT BE SOMETHING ON THE PERSON END IM EMAILING BUT NO ONE ELSE IN THE COMPANY HAS THIS PROBLEM.
Jess-Q 12,795 Reputation points Microsoft External Staff Moderator

2025-10-22T15:29:09.0466667+00:00
Hi @Stephen Hobbs,

Thank you for the response.

If your IT department has verified that the issue is isolated to your account and potentially related to the other party, and not affecting other users, I recommend requesting your IT administrator to escalate the matter by opening a ticket with Microsoft support for further investigation.

This will allow Microsoft engineering team to investigate the problem more deeply, especially since it may stem from backend infrastructure or service-level configurations.

A technical support engineer from Microsoft can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.

Here’s what your Office 365 Global Admin (IT Admin) should do next:   

Submit a Service Request: The Global Admin should create a service request with Microsoft support to get advanced technical assistance and diagnostics. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin.   

Note: If you’re an end-user, please coordinate with your Office 365 Global Administrator to handle these steps. 

I apologize for redirecting you the related team support, as the moderators in this community don’t have access to the detailed system needed to troubleshoot this effectively due to privacy and security constraints. But Microsoft’s support team has elevated permissions and access to backend systems that we, as community moderators, do not. This ensures your issue is handled with the right tools and expertise and helps you get a faster resolution.

Hopefully they will be able to help with your issue and if you have any other questions or need further assistance, feel free to ask.
Jess-Q 12,795 Reputation points Microsoft External Staff Moderator

2025-10-27T15:06:54.93+00:00

Hi @Stephen Hobbs,

It has been a while and I am writing to see how things are going with this issue. Have you had a chance to check the replies provided? Any update would be appreciated.