Why are emails I send to some outlook email addresses being sent back undeliverable

Question

(reason: 550 5.7.515 Access denied, sending domain doesn't meet the required authenticatio...<Removed PII>] [AM4PEPF00025F9C.EURPRD83.prod.outlook.com 2026-02-12T09:12:23.463Z <Removed PII>])

Answer 1

Hi @nicolahopkins,

Welcome to Microsoft Q&A, and thank you very much for reaching out.

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.

Based on your description, from my research, as Q&A assist mentioned, this error typically occurs when your domain does not meet the required email authentication standards for sending a high volume of email to Microsoft consumer email services.

To address this, please review your email authentication configuration and ensure that SPF, DKIM, and DMARC are set up correctly.

Additionally, if you are sending bulk or marketing emails, please note that Exchange is not designed for bulk email delivery. In such cases, using a dedicated bulk email service would be more appropriate.

Microsoft has also provided a documentation that specifically covers this issue, which you may find helpful to review.

I hope this helps.

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Answer 2

The error message you are encountering, "550 5.7.515 Access denied, sending domain doesn't meet the required authentication," typically indicates that the email domain you are using to send messages is failing to meet the necessary authentication standards set by Microsoft. This can happen due to issues with SPF (Sender Policy Framework) records or DKIM (DomainKeys Identified Mail) settings, which are essential for verifying that the email is coming from a legitimate source.

To resolve this issue, you should check the following:

1. SPF Records: Ensure that your domain's SPF record is correctly set up to include the IP addresses of the servers that are allowed to send emails on behalf of your domain.
2. DKIM Settings: If you are using DKIM, make sure it is properly configured for your domain.
3. Domain Reputation: Sometimes, if your domain has been flagged for sending spam or other malicious content, it may be blocked from sending emails to certain addresses.

You may also want to consult with your domain administrator or email service provider to ensure that all necessary authentication measures are in place.

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References:

• External senders - Use the delist portal to remove yourself from the blocked senders list and address 5.7.511 Access denied errors
• Microsoft 365 throttled traffic from my IP address