The requirements, in Microsoft's words
- High-volume threshold
- 5,000+ messages per day to consumer Outlook.com/Hotmail/Live addresses = high-volume sender
- Authentication
- SPF must pass
- DKIM must pass
- DMARC required, p=none minimum, aligned with SPF or DKIM
- Spam rate
- No numeric threshold published in the announcement; SNDS/JMRP complaint data used
- Unsubscribe
- An easy, visible opt-out is recommended; an RFC 8058 header mandate is not stated in the accessible announcement
- Also
- Valid From/Reply-To; List hygiene / bounce management; Transparent headers
- Enforcement
- : Non-compliant mail from high-volume senders rejected with 550 5.7.515 Access denied, sending domain does not meet the required authentication level (previously routed to Junk)
- Rejection codes
- 550 5.7.515 Access denied, sending domain [domain] does not meet the required authentication level
- 550 5.7.509 sending domain does not pass DMARC verification
- 550 5.7.511 Access denied, banned sender
- 550 5.7.606-649 banned sending IP (S3140)
Check your domain against them
Authentication is the half you can verify yourself in a minute. Theemail auth checker reads SPF, DKIM, DMARC and its alignment mode, the MX records and reverse DNS straight from DNS, and names what is missing. Complaint rate and one-click unsubscribe are the halves only the receiver and the message itself can answer: Postmaster Tools for the first, the message headers for the second.
SPF, DKIM and aligned DMARC
Microsoft's standard is the same three records Google and Yahoo require, with the same catch. SPF must pass for the sending domain. DKIM must pass. DMARC must exist, p=none at minimum, and the From domain must align with the domain that passed SPF or DKIM. A message signed by your sending platform's domain rather than yours passes DKIM and fails alignment, and Microsoft rejects it with 550 5.7.509 (does not pass DMARC verification) or 550 5.7.515.
- 1
Publish or repair the records
The SPF, DKIM and DMARC generators produce the exact TXT records; DKIM comes from your sending platform's console.
- 2
Verify after propagation
The auth checker reads all three and flags a missing DMARC policy, an over-limit SPF record and a weak DKIM key.
- 3
Confirm alignment on a real message
Send to yourself, paste the headers into the header check above, and read the alignment row. This is the step that catches a platform signing with its own domain.
What the rejection looks like
Before non-compliant mail from high-volume senders was routed to Junk. Since then Outlook.com refuses it at the gateway: 550 5.7.515 Access denied, sending domain [SendingDomain] does not meet the required authentication level, which the sending server returns as a bounce. Two other codes sit beside it: 550 5.7.511 (banned sender) and 550 5.7.606 (banned sending IP), which are reputation verdicts rather than authentication failures and are the ones warming has something to do with.
SNDS and the Junk Mail Reporting Program
- SNDS (Smart Network Data Services): the reputation and complaint data Microsoft holds on your sending IPs, per IP. On Microsoft 365 or Google Workspace the IPs are the provider's and shared; on your own server or a relay they are yours to register.
- JMRP (Junk Mail Reporting Program): a copy of every complaint an Outlook.com user files against your mail, so the address can be removed the same day.
- What neither shows: where a given message landed. The Free Deliverability Test reports placement at Outlook.com and Microsoft 365 alongside Gmail and Yahoo.
Outlook.com and Microsoft 365 are different receivers
The high-volume rule is scoped to consumer addresses. A Microsoft 365 tenant receives through Exchange Online Protection with the tenant's own anti-spam and DMARC policies, which can quarantine or reject a DMARC failure at any volume. For a B2B sender the practical rule is the same: the three records aligned, then reputation. For what a tenant's filtering does with a young domain, see Microsoft 365 warmup.
Beyond compliance
Google's and Yahoo's rules, which the same message has to meet, are on Gmail and Yahoo bulk sender requirements (2026).