Outgoing emails are undelivered

Question

Outgoing emails are undelivered

Lerron Little 0

I send bulk emails once a week to 50-100 people. These emails are undelivered and I receive the following message.

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.

For more information and tips to fix this issue see this article: https://go.microsoft.com/fwlink/?LinkId=389361.

How can I set up delivery of bulk emails

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Answer 1

Hi Lerron Little

The error 550 4.4.7 generally indicates that Microsoft 365 was unable to establish or maintain a connection with the recipient's mail server, and the message could not be delivered after multiple retry attempts. The NDR you received already references Microsoft's troubleshooting article for this error.

Since the message states that the recipient's email system is not accepting connection requests, the issue is often on the receiving mail system rather than with Outlook or Microsoft 365. The recipient's email administrator may need to review their mail server, DNS/MX records, connectivity, or mail filtering configuration.

If you are the Microsoft 365 administrator, could you check the Message Trace details for one of the affected messages and let us know what status or error is shown there? The Message Trace results may provide additional information about where the delivery attempt timed out and whether the issue is affecting all recipients or only specific domains. If you are not administrator, you can reach out to your organization's IT administrator for help.

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