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550 5.7.515: access denied by Outlook.com

Outlook.com, Hotmail and Live refuse mail from high volume senders whose domain lacks SPF, DKIM and DMARC. The bounce names the domain that has to be fixed.

Updated 2 min read

On this page (7)

550 5.7.515 is a permanent SMTP reply: sender rules at Outlook.com. This page is part of our SMTP error code reference, where every code links to the RFC and to what Gmail, Outlook and Yahoo publish about it.

Kind
Permanent: sending the same message again fails the same way
Retry by hand
No, fix the cause first
In Mailbay
bounced, address not suppressed

What 550 5.7.515 means

5.7.515 is a Microsoft code and is not in the IANA registry of enhanced codes [1]. Its class and subject follow RFC 3463: 5 is permanent and 7 is the security or policy subject [2].

The Mailbay domain setup step listing the DNS records to publish for example.com, each with a live status and a plain language fix
Mailbay's domain setup checks each record live and says what to change. Here example.com has none of them yet: 0 of 6 records live, with MX, SPF and the rest listed.

What Gmail, Outlook and Yahoo say

Outlook.com
The full error is "550 5.7.515 Access denied, sending domain <domain> does not meet the required authentication level." It applies when "You send 5,000 or more email messages to Microsoft consumer email services" with the same From domain. Then "Both SPF and DKIM checks must pass", a DMARC record of at least p=none must exist, and messages must pass DMARC [3]. The postmaster site dates the rule from May 5, 2025 [4].
Gmail and Yahoo
Have similar rules for bulk senders with their own codes: Gmail since February 1, 2024 [5], Yahoo requiring that "DMARC must pass" [6]. See 550 5.7.26.

Sources, read on October 14, 2026

  1. [1]IANA, SMTP Enhanced Status Codes registry: www.iana.org/assignments/smtp-enhanced-status-codes/smtp-enhanced-status-codes.xhtml
  2. [2]RFC 3463, Enhanced Mail System Status Codes: www.rfc-editor.org/rfc/rfc3463
  3. [3]Microsoft Support, Fix NDR error 550 5.7.515 in Outlook.com: support.microsoft.com/en-us/outlook/fix-ndr-error-550-5-7-515-in-outlook-com
  4. [4]Outlook.com Postmaster: substrate.office.com/ip-domain-management-snds/postmaster
  5. [5]Google, Email sender guidelines: support.google.com/a/answer/81126
  6. [6]Yahoo Sender Hub, best practices: senders.yahooinc.com/best-practices/

Prices change. If something here is out of date or wrong, email hello@mailbay.dev and we will fix it.

Common causes

  • A domain with SPF but no DKIM, or DKIM but no SPF: Microsoft wants both to pass.
  • No DMARC record on the From domain.
  • SPF and DKIM pass, but for a different domain than the From address, so DMARC fails.

How to fix it

  1. Publish SPF and DKIM for the From domain and make sure both pass on a test message.
  2. Publish _dmarc with at least v=DMARC1; p=none and a report address.
  3. Send a test email to the deliverability test to confirm SPF, DKIM and DMARC all pass before resuming volume.

How Mailbay reports it

When a recipient's server answers 550 5.7.515 to mail you send through Mailbay, the recipient becomes bounced and you get a message.bounced event with the server's reply in response and permanent: false. The message statuses page lists every state.

A policy refusal says nothing about whether the address exists, so Mailbay does not suppress it, and it does not count toward the automatic pause, which only counts hard bounces and spam complaints.

A domain verified in Mailbay has all three: the SPF include, a DKIM key that signs your mail, and a DMARC record, each checked live in the setup step below (domains).

Terminal output of dig TXT for the _dmarc records of gmail.com, yahoo.com and outlook.com
The DMARC records Gmail, Yahoo and Outlook publish for their own domains, read with dig on October 14, 2026: Yahoo rejects mail that fails DMARC, the other two monitor.

Related codes

  • 550 5.7.26: failed SPF, DKIM or DMARC, permanent.
  • 550 5.7.25: no reverse DNS for the IP, permanent.
  • 550 5.7.1: refused for a policy reason, permanent.
  • 421 4.7.0: temporary refusal, connection closed, temporary.
  • 550 5.1.1: mailbox does not exist, permanent.

Seeing an API error rather than an SMTP code? Mailbay's own errors, each with a fix, are on the errors page.

Questions

Does 550 5.7.515 apply if I send fewer than 5,000 emails a day?

Microsoft states the rule for senders of 5,000 or more messages a day to its consumer services with the same From domain. Publishing SPF, DKIM and DMARC is worth doing at any volume.

Is DMARC p=none enough for Outlook.com?

Microsoft's example record is v=DMARC1; p=none. The messages still have to pass DMARC, so SPF or DKIM must align with the From domain.

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