Hotmail can't received e-mail from our customer's e-mail.

The senders’ mail administrators must correct their domains’ SPF, DKIM, and DMARC authentication because Hotmail is rejecting these messages at the server before they reach your mailbox.

The response:

550 5.7.1 Message rejected: Message lacks SPF/DKIM/DMARC Auth Records (AS9031519)

indicates a mail-authentication rejection, not a problem with Classic Outlook on your Windows PC. A 550 5.7.1 response can occur when SPF is incomplete or the destination’s authentication requirements are not met.^1^

What each affected sender must do

Send the complete non-delivery report (NDR/bounce message) to that sender’s email administrator or email provider. Remove personal addresses first, but preserve the status code, sending domain, timestamps, and authentication results.

Their administrator should:

1. SPF: Ensure the sending domain has one valid SPF record that authorizes every service and IP address sending its mail.
2. DKIM: Enable DKIM signing and verify that the public DNS key matches the signature applied to outgoing messages.
3. DMARC: Publish a valid DMARC record.
4. Alignment: Ensure SPF or DKIM aligns with the domain shown in the visible From address, as required by DMARC.
5. If they use a marketing platform, relay, hosting provider, or security gateway, ensure that service is included in SPF and signs with the sender’s domain.
6. After DNS changes propagate, send a new message directly to your Hotmail address and confirm it is accepted.

Microsoft identifies the sender as responsible for correcting failed SPF/DKIM authentication and domain alignment.^2^

You do not need to add SPF, DKIM, or DMARC records for your @hotmail.com address; Microsoft manages the Hotmail domain. Adding these senders to Safe Senders is also unlikely to help because the message is rejected during SMTP delivery, before it reaches your mailbox.^3^

Because several senders are affected

Determine whether the senders use:

• The same company/domain,
• The same mail-hosting provider, or
• Completely unrelated domains and providers.

If they share a domain or provider, that administrator should investigate the common sending configuration.

If several unrelated domains/providers receive the same AS9031519 authentication rejection:

1. Collect one complete NDR from each unrelated sender.
2. Sign in to Hotmail using Outlook.com in a browser.
3. Select Help on the menu bar and enter the problem.
4. Scroll to Still need help? and select Yes.
5. Include the sanitized NDRs and explain that unrelated sending domains are receiving the same rejection.

This is the documented Outlook.com support route when normal receiving checks do not resolve the issue.^4^

For urgent communication, ask affected customers to use an alternative email account until their domain authentication is corrected.

References

1. Troubleshoot email authentication in Microsoft 365
2. Security Operations guide for email authentication in Microsoft 365
3. Incoming emails being blocked due to lack of SPF/DKIM/DMARC records on my @outlook.com account - Microsoft Q&A
4. Can't send or receive email in Outlook.com | Microsoft Support