If you send 5,000 or more messages to Microsoft consumer email services using the same domain in the visible 5322.From address, Microsoft treats you as a high-volume sender. To avoid authentication-based rejection, publish SPF, DKIM and DMARC for that domain, make sure SPF and DKIM checks pass, and ensure DMARC passes with at least one of those mechanisms aligned to the visible From domain. This requirement covers Outlook.com, Hotmail, Live.com and MSN consumer mailboxes.
When Microsoft’s high-volume rules apply
Microsoft defines a high-volume sender by two conditions together:
- You send 5,000 or more messages to Microsoft consumer email services.
- Those messages use the same domain in the
5322.Fromaddress—the address recipients see in the From field.
The guidance does not define this as 5,000 messages per day. It also depends on mail delivered to Microsoft consumer services, not simply on whether your email platform labels your account “bulk.”
If your traffic meets both conditions, evaluate the authentication of the domain shown in 5322.From. A different envelope sender or a provider-owned signing domain does not by itself satisfy the requirement.
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The authentication records Microsoft expects
SPF: authorize the actual sending source
Publish an SPF record for the domain used by the message’s 5321.MailFrom identity (the envelope sender). The record must authorize the servers or service that actually transmit your mail, and the SPF check must pass.
If SPF is the mechanism that supplies DMARC alignment, the 5321.MailFrom domain must align with the domain in 5322.From. Authorizing a provider while using an unrelated visible From domain can leave DMARC unaligned.
DKIM: sign with your domain
Enable DKIM signing for your messages and verify that the DKIM check passes. When DKIM supplies DMARC alignment, the domain in the valid DKIM signature must align with the 5322.From domain.
A platform’s default DKIM signature may authenticate the platform rather than your organization. Configure a custom signing domain when necessary, then confirm the signed domain in the received headers.
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Publish a DMARC TXT record at the _dmarc hostname. Microsoft gives v=DMARC1; p=none as an example value. The troubleshooting guidance also identifies p=none, p=quarantine and p=reject as valid policy values; it does not require one specific policy among those three.
DMARC must pass through SPF and/or DKIM, with at least one passing mechanism aligned to the visible 5322.From domain. Publishing a record is not enough if the identities used by the message do not align.
How the three checks fit together
| Check | What must pass | Identity to compare with 5322.From |
|---|---|---|
| SPF | The sending source is authorized for the 5321.MailFrom domain. |
5321.MailFrom must align if SPF is used for DMARC. |
| DKIM | The message has a valid DKIM signature. | The DKIM signing domain must align if DKIM is used for DMARC. |
| DMARC | A DMARC record exists and DMARC passes. | At least one passing SPF or DKIM result must align with 5322.From. |
Under Microsoft’s stated high-volume requirements, both SPF and DKIM checks are expected to pass, while DMARC must pass through at least one aligned mechanism.
Fixing a 550 5.7.515 rejection
The bounce text is: 550 5.7.515 Access denied, sending domain <domain> does not meet the required authentication level.
Microsoft explains that the sender’s domain in the 5322.From address does not meet the authentication requirements defined for the sender. Treat this as an authentication failure first, rather than assuming message content or sending volume caused it.
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Read the non-delivery report
Record the domain shown in the error and compare it with the visible From address your application generated. That is the domain Microsoft is evaluating.
-
Inspect the message headers
Open the rejected message’s headers using Outlook’s header view. Locate the Authentication-Results information and note whether SPF, DKIM and DMARC passed or failed, along with the domains each result evaluated.
-
Verify SPF authorization
Check that the actual sending service is authorized for the
5321.MailFromdomain. If SPF is intended to provide DMARC alignment, confirm that this envelope-sender domain aligns with5322.From. Correct the DNS record or the envelope-sender setting supplied by your mail service, then send a new test. -
Verify DKIM signing and alignment
Confirm that the message contains a valid DKIM signature and identify its signing domain. If DKIM is the aligned mechanism, configure the service to sign with a domain aligned to
5322.From, not only with the provider’s default domain.Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy. -
Verify the DMARC record and result
Confirm that a DMARC TXT record is published at
_dmarc, contains a valid policy such as one of the values Microsoft lists, and produces a DMARC pass. At least one of the passing SPF or DKIM results must align with the visible From domain. -
Audit every third-party sender
For each marketing platform, CRM, transactional service or other relay, verify that the envelope
5321.MailFromuses your domain, the service’s sending IPs or required include values are authorized by SPF, DKIM signs with your domain, and DMARC evaluates the sender’s domain. Repeat this audit for every service that can send with the same visible From domain.
Common configurations that still fail
SPF passes but DMARC fails
This usually means the authorized envelope domain and the visible From domain differ. SPF authentication alone does not create DMARC alignment.
DKIM passes but DMARC fails
The signature may be valid yet use a provider-owned domain. DMARC requires the signing domain to align when DKIM is the mechanism being used.
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DMARC is published but does not pass
A DNS record at _dmarc is only the policy declaration. The message still needs a passing SPF or DKIM result, and at least one passing result must align with 5322.From.
Only some streams are authenticated
Authentication can be correct for one platform and missing for another. Inventory all systems allowed to send as the domain, including less-visible automated or support-mail systems, and check each stream’s headers separately.
What compliance does—and does not—solve
Meeting the stated SPF, DKIM and DMARC conditions addresses the authentication requirement associated with a 550 5.7.515 rejection. Microsoft does not promise that authentication alone guarantees inbox placement or delivery. After the authentication results pass, continue to monitor bounces, reputation and message quality, but do not substitute those broader deliverability tasks for fixing a failed authentication result.
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