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Fix Cannot Send Email but Can Receive Messages in Outlook
Question details
The user is unable to send new emails or reply to messages, despite being able to receive them, and is receiving an undeliverable error message.
- Product
- Microsoft Outlook / Exchange Online
- Device & OS
- not provided
- Scenario
- Attempting to send a new email or reply to a message using a custom domain on Microsoft 365.
- Observed behavior
- Outgoing emails fail to send and immediately return a Non-Delivery Report (NDR) with an undeliverable error, even when sending to the user's own email address.
Before altering administrative settings, check your Outbox to ensure no large attachments are blocking the queue, and verify that your device has a stable internet connection.
Review the Non-Delivery Report (NDR) and Test via Webmail
Identify the exact cause of the failure using the error code provided in the bounce-back message and isolate desktop app issues.
A Non-Delivery Report (NDR) contains specific diagnostic codes that explain why an email failed to send. Testing on the web helps determine if the issue is with your local Outlook client or the email account itself.
Locate the bounce-back email in your inbox and open it to view the full undeliverable message.
Look for the specific status code (e.g., 5.x.x) and the accompanying explanation text to understand the exact delivery block.
Open your web browser and sign in to Outlook on the web (OWA) using your Microsoft 365 credentials.
Compose a new email and send it to yourself or a trusted contact to see if the issue is limited to the desktop client.
Verify Exchange Online DNS Records
Ensure your custom domain's DNS settings are correctly configured for Microsoft 365 to allow outgoing mail routing.
Run a Message Trace (Admin Only)
Microsoft 365 administrators can track the email's path to find exactly where and why the delivery failed.
Seamless Document Management with WPS Office
While troubleshooting your Microsoft 365 email delivery issues, you can continue preparing your important attachments and documents using WPS Office. It provides a lightweight, highly compatible, and free alternative to Microsoft Office.
- 1. Download the Installer: Visit the official WPS website and click the free download button to get the latest version.
- 2. Install WPS Office: Run the downloaded setup file and follow the on-screen instructions to quickly install the software.
- 3. Open and Edit: Launch WPS Office, open your existing Microsoft Office files, and continue working without interruptions.
Frequently Asked Questions
What is a Non-Delivery Report (NDR)?
An NDR is an automated bounce message from a mail server informing the sender that an email could not be delivered. It usually includes a specific error code that helps diagnose the failure.
Why can I receive emails but not send them?
This typically points to an issue with your Outgoing Mail Server (SMTP) settings, incorrect DNS records (like SPF), or specific mailbox sending limits, while the incoming server (IMAP/POP/Exchange) remains perfectly functional.
How do I fix the 'undeliverable' error when emailing myself?
Check if your custom domain's Exchange Online DNS records are correct. Self-routing loops, incomplete domain verification, or strict anti-spoofing policies can block internal messages if the setup is incomplete.
