Outlook high-volume sender requirements
Microsoft's rules, enforced from May 5, 2025, for domains sending over 5,000 messages a day to Outlook.com, hotmail.com and live.com: SPF, DKIM and DMARC.
What it means
Microsoft announced the requirements on April 2, 2025, for Outlook.com, its consumer service covering hotmail.com, live.com and outlook.com addresses. Domains sending more than 5,000 emails a day must pass SPF, pass DKIM, and publish DMARC with at least p=none, aligned with SPF or DKIM (preferably both).
The original plan routed non-compliant mail to Junk first. An April 29 update changed the action to rejection with 550 5.7.515, "Access denied, sending domain does not meet the required authentication level", from May 5, 2025.
Microsoft also recommends valid From and Reply-To addresses that can receive replies, a functional unsubscribe link, removing invalid addresses and transparent practices with consent, and reserves the right to filter or block non-compliant senders.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- Microsoft Tech Community: Outlook's requirements for high-volume senderstechcommunity.microsoft.com
- Outlook.com Postmastersendersupport.olc.protection.outlook.com
All 432 terms in the glossaryThe wiki: blocklists and bounce codes