How to Fix this 550 5.7.515 — SPF: Pass / DKIM: Fail / DMARC: Pass

Question

Dear Microsoft Email Support Team,

We are contacting you from the IT Department of [Moderator note: Personally Identifiable Information removed]. regarding an incoming message rejected during delivery to [Moderator note: Personally Identifiable Information removed] @safwaest.com, [Moderator note: Personally Identifiable Information removed] @safwaest.com, [Moderator note: Personally Identifiable Information removed] @safwaest.com, [Moderator note: Personally Identifiable Information removed] @outlook.com, [Moderator note: Personally Identifiable Information removed] @outlook.com, [Moderator note: Personally Identifiable Information removed] @outlook.com

The message contained a SAP Ariba invitation to register our company as a supplier with ***[***Moderator note: Personally Identifiable Information removed]

The non-delivery report shows that Microsoft rejected the message at the end of the SMTP DATA command, with the following details:

• Sending domain: [Moderator note: Personally Identifiable Information removed]
• Receiving server issuing the rejection: [Moderator note: Personally Identifiable Information removed]
• Receiving server IP address: [Moderator note: Personally Identifiable Information removed]
• Rejection timestamp: 2026-09-21T07:53:07.954Z
• Error code: 550 5.7.515
• Authentication results: SPF: Pass / DKIM: Fail / DMARC: Pass
• Diagnostic reference: [Moderator note: Personally Identifiable Information removed]

The reported rejection reason was:

“Access denied, sending domain KSAPRV.CLOUD.ARIBA.COM doesn't meet the required authentication level.”

Please review the available authentication diagnostics and identify the specific reason for the DKIM Fail result, including whether it relates to DNS key retrieval, signature verification, or a message body hash mismatch.

Please clarify the corrective action required from SAP Ariba as the sending service provider, whether any action is required on the receiving side, and what additional message data or evidence is needed to complete the investigation.

Kindly provide a support case reference and the recommended next steps to resolve the issue and verify successful delivery on a subsequent attempt.

Kind regards,

IT Department

[Moderator note: Personally Identifiable Information removed]

Answer 1

Hi @Imran Saleem,

Just to gently clarify before going any further, this community forum is separate from Microsoft Support. Forum users, moderators, and Microsoft staff participating here do not have access to internal mail-flow logs, support case systems, or the tools required to investigate or resolve this issue directly. However, I am happy to help explain the error and point you in the right direction.

The NDR indicates that Microsoft rejected the message because the sending domain did not meet the required authentication level. Although DMARC passed through aligned SPF, Microsoft reports that DKIM failed. If the sending domain is classified as a high-volume sender to Outlook.com, Microsoft requires SPF, DKIM, and DMARC compliance.

Please ask the sender to review the following Microsoft guidance and verify the DKIM configuration with their email administrator or service provider: Fix NDR error “550 5.7.515” in Outlook.com

I hope this information helps clarify the cause of the rejection and the recommended next steps. Thank you for your patience.