Email bouncing

Question

Email bouncing

Theresa Park 0

Microsoft 365 Email Delivery – Outgoing Emails Bouncing

I am experiencing an issue with email delivery from my Microsoft 365 business email account. Several people have told me that emails I send are bouncing back or not being delivered.

I need assistance troubleshooting the cause of the bounced emails and verifying that my Microsoft 365/Exchange Online email account, domain, DNS records, and mail-flow settings are configured correctly.

Please investigate whether there are any restrictions, blocks, authentication issues, reputation issues, or other problems affecting outgoing email delivery.

I would also like to know what information or bounce-back/error messages you need from me to determine the cause.

This is affecting my ability to communicate reliably from my business email account, so I would appreciate help identifying and resolving the issue.

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2 answers

Your answer

Answer 1

For outgoing email bounces in Microsoft 365, use this order to isolate the cause:

Check whether the problem is only in Outlook or the local mail app.
- Sign in to Outlook on the web and test sending from there.
- If mail works in Outlook on the web but not in the installed app, the issue is likely the local Outlook profile or app rather than Exchange Online.
Run Microsoft Support and Recovery Assistant on the affected computer.
- This is recommended as a first troubleshooting step for Outlook or Microsoft 365 issues affecting a single user.
- It can detect and help fix Outlook profile, account, and related client issues.
- It is not available for new Outlook for Windows.
If admin access is available, check Microsoft 365 service health.
- In Microsoft 365 admin center: Admin > Service health > View the service health.
- If Exchange Online is degraded, outbound delivery can be delayed and no separate service request is needed while the incident is active.
Run the email delivery troubleshooter.
- In Microsoft 365 admin center, launch Diag: Troubleshoot Email Delivery.
- Enter the sender and recipient addresses and run the tests.
- This requires a Microsoft 365 administrator account.
- It is not available for Microsoft 365 Government, Microsoft 365 operated by 21Vianet, or Microsoft 365 Germany.
Run a message trace for a failed message.
- In Exchange admin center: mail flow > message trace.
- For Microsoft 365 Small Business admin: Admin > Service settings > Email, calendar, and contacts > Email troubleshooting > Troubleshoot message delivery.
- Message trace is the main tool to confirm what happened to a specific outbound message and whether it was delivered, delayed, or failed.
If the bounce message is 550 5.7.23, check SPF configuration.
- Verify the SPF DNS record for the domain.
- Provision all owned domains.
- Add any on-premises sending IPs to the SPF record if mail is sent for those domains through Microsoft 365 or Office 365.
- Check whether the outbound message was identified as spam and routed through the High Risk Delivery Pool. If it was incorrectly detected as spam, contact support.

What information is needed to determine the cause:

The full non-delivery report or bounce message.
The exact error code, especially anything like 550 5.7.23.
The sender and recipient addresses used in the failed test.
Whether the message fails from Outlook on the web, desktop Outlook, or both.
The approximate time the failed message was sent, so it can be checked in message trace.

A practical first path is:

Test in Outlook on the web.
Run Support and Recovery Assistant if the issue appears user-specific.
If admin access is available, check Service health.
Run Diag: Troubleshoot Email Delivery.
Run message trace on one failed message.
If the NDR shows 550 5.7.23, review SPF and outbound spam handling.

Answer 2

Elena-VH 1,325 Independent Advisor

Dear Theresa Park,

I understand your concern. As a forum user, I can't directly investigate your tenant or mail flow, but I can help narrow down the cause. To identify why outgoing emails are bouncing, could you please provide:

Are all recipients affected, or only recipients at specific external domains?
Are all users in your organization affected, or only certain mailboxes?
Do you receive a Non-Delivery Report (NDR) or bounce-back message? If yes, please share the full error code and diagnostic details (remove any personal information if needed). For more information, please refer to Email nondelivery reports and SMTP errors in Exchange Online

Moreover, according to my research, there is currently an incident in Exchange Online (EX1464935) affecting some Microsoft 365 users. This issue may cause users to be unable to connect to Exchange Online or experience degraded functionality, including potential mailbox access, authentication, and email service-related problems.

Because of this ongoing service incident, it is possible that the bounced emails or delivery issues you are experiencing could be related to the broader Exchange Online service disruption rather than a configuration problem within your tenant.

In this case, if you are a user, please contact your IT admin and ask them to report the issue through the Microsoft 365 admin center. The administrator can also check the service status dashboard (Microsoft 365 Admin Center > Health > Service Health) to see the latest updates and confirm if other users in their organization are experiencing the same issue. For your reference: https://admin.microsoft.com/adminportal/home?#/servicehealth

If needed, your IT Admin can also open a support case with Microsoft through the Microsoft 365 Admin Center for further investigation. If you don't know who your IT admin is, see this article: How do I find my Microsoft 365 admin? - Microsoft Support.

I hope the information shared is helpful. If you have any questions or if I have misunderstood anything, please feel free to reach out. Looking forward to your update.

Theresa Park 0 Reputation points

2026-08-31T18:28:21.4666667+00:00

I cant share the email that people are receiving when they try to email me as I am not getting any emails from them so even forwarded emails are bouncing
Elena-VH 1,325 Reputation points Independent Advisor

2026-08-31T18:50:48.78+00:00
Dear Theresa Park,

Since you don't have access to the bounce message, could you ask one of the affected senders to provide just the error code or a screenshot of the Non-Delivery Report (NDR)? ‌(Remember to remove any personal information before sharing)

Moreover, could you also let me know:

Are you able to send emails successfully to others?

Are you able to receive emails from users within the same organization?

Whether the people who are reporting the bounced emails are users within the same Microsoft 365 tenant as you, or are they external users from different organizations/domains?

Are other users in the same tenant also unable to receive emails, or is the problem limited to your mailbox?‌

Currently, there is an ongoing Exchange Online incident (EX1464935); the symptoms you're experiencing may be related to that service issue. Exchange Online incidents can impact email delivery, mailbox access, mail flow processing, and other Exchange-related functionality.

Therefore, could you please let me know when this issue first started occurring? and Have you and the affected people contacted the organization's IT administrator about this issue?

The IT Admin can check the Exchange Online Message Trace to identify whether the messages are being blocked, deferred, or rejected and to review any recent changes to mail flow rules, connectors, or outbound spam policies.‌ For more information, please follow: Message trace in the Exchange admin center in Exchange Online

Note: I apologize, but as a forum user, I do not have access to your environment and therefore cannot directly investigate the issue or determine the exact root cause.
Theresa Park 0 Reputation points

2026-09-01T00:58:31.15+00:00

Here is the error message that my friend received
Theresa Park 0 Reputation points

2026-09-01T00:59:52.1533333+00:00
Elena-VH 1,325 Reputation points Independent Advisor

2026-09-01T03:39:28.5+00:00

Dear Theresa Park,

Thank you for sharing the screenshot.

Based on the information shown, I can see that there is currently a delivery delay issue, and these tenants are also affected by the ongoing Exchange Online incident (EX1464935). Because this service incident may impact Exchange Online functionality, including email delivery and mailbox access, it is possible that the behavior you and other people are experiencing is related to the ongoing Microsoft service issue.

In this case, if you are a user, please contact your IT admin and ask them to report the issue through the Microsoft 365 admin center. The administrator can also check the service status dashboard (Microsoft 365 Admin Center > Health > Service Health) to see the latest updates and wait for Microsoft to implement a fix. For your reference: https://admin.microsoft.com/adminportal/home?#/servicehealth

Once Microsoft confirms that the incident has been resolved, please test email sending and receiving again. If the problem continues after the incident is closed, further investigation of your domain configuration, DNS records, and mail flow settings would be recommended.

If needed, the IT Admin can also open a support case with Microsoft through the Microsoft 365 Admin Center for further investigation. For reference: Get support for Microsoft 365 for business

If you don't know who your IT admin is, see this article: How do I find my Microsoft 365 admin? - Microsoft Support.

Thank you for your patience while Microsoft works to resolve the service issue.