Microsoft has implement stricter email deliverability requirements for all bulk email senders from May 5, 2025. This move mirrors the sender policy enforcement already adopted by Gmail and Yahoo in 2024 and aims to strengthen email authentication, reduce spam, and protect inbox integrity across Outlook, Hotmail, Live, and MSN domains.
Key Requirements for Senders:
To maintain inbox placement and avoid delivery issues, bulk senders must comply with the following:
==>SPF (Sender Policy Framework)
Ensure a valid SPF record that authorizes your sending IPs and platforms (e.g., SendGrid, Amazon SES).
==>DKIM (DomainKeys Identified Mail)
Emails must be DKIM-signed to confirm authenticity and prevent tampering.
==>DMARC (Domain-based Message Authentication, Reporting & Conformance)
A published DMARC policy is mandatory. At minimum: p=none, with proper alignment of the From domain with SPF or DKIM (ideally both).
==>Valid “From” and “Reply-To” Addresses
Both must point to real, functional inboxes that can accept replies. Microsoft explicitly discourages the use of dummy, blackholed, or unmonitored addresses like noreply@.
==>Local Parts (Before the @) to Avoid:
noreply@, admin@, root@, postmaster@, donotreply@, test@, spam@, bulk@, marketing@ (if not aligned), mailer@, info@ (if unmonitored), support@ (if fake)
==>Recommended Email Identities:
[email protected], news@, updates@, reply@, contact@, [email protected]
==>Applies To All Microsoft Consumer Domains:
Including but not limited to: hotmail.com, live.com, outlook.com, msn.com, and over 50 regional variants (hotmail.be, hotmail.ch, hotmail.co.id, hotmail.co.il, hotmail.co.jp, hotmail.co.kr, hotmail.com, hotmail.com.ar, hotmail.com.au, hotmail.com.br, hotmail.com.hk, hotmail.com.tr, hotmail.com.tw, hotmail.com.vn, hotmail.co.nz, hotmail.co.th, hotmail.co.uk, hotmail.co.za, hotmail.cz, hotmail.de, hotmail.dk, hotmail.es, hotmail.fi, hotmail.fr, hotmail.gr, hotmail.it, hotmail.my, hotmail.no, hotmail.ph, hotmail.rs, hotmail.se, hotmail.sg, live.at, live.be, live.ca, live.cl, live.cn, live.co.kr, live.com, live.com.ar, live.com.au, live.com.mx, live.com.my, live.com.ph, live.com.pt, live.com.sg, live.co.uk, live.co.za, live.de, live.dk, live.fr, live.hk, live.ie, live.in, live.it, live.jp, livemail.tw, live.nl, live.no, live.ru, live.se, microsoft, msn.cn, msn.com, outlook.com, windowslive.com)
==>What need to test:
audit your SPF, DKIM, and DMARC configurations.
Review your sending addresses(from & Reply-To ) and ensure replies are accepted.
Avoid using placeholder, fake, or unmonitored inboxes.
| Requirement | Gmail | Microsoft (Outlook.com) |
|---|---|---|
| Authentication Volume Threshold | 5,000+ messages/day to Gmail, Yahoo doesn’t hold to a strict number but it is in the ballpark of 5000. | 5,000+ messages/day to Outlook.com, Hotmail.com, Live.com |
| SPF (Sender Policy Framework) | Required | Required |
| DKIM (DomainKeys Identified Mail) | Required | Required |
| DMARC Policy | Required. Minimum policy: p=none. Must align with SPF or DKIM. | Required. Minimum policy: p=none. Must align with SPF or DKIM. |
| One-Click Unsubscribe (RFC 8058) | Required. Bulk senders must include RFC 8058-compliant unsubscribe. | Unsubscribe link required. RFC 8058 not required |
| List Unsubscribe Header | Required. Must support List-Unsubscribe header with both mailto: and URL. | Not explicitly required. |
| Spam Rate Threshold | Required. Must stay below Gmail/Yahoo’s spam complaint thresholds of 0.3% | No threshold defined, required to have clean lists and enforce best practices. Non compliant senders may experience negative action. |
| TLS (Transport Layer Security) | Required. Emails must be sent over TLS. | Not mentioned in Microsoft’s latest policy updates. |
| Valid HELO/EHLO | Required. Must not use a dynamic IP or malformed hostname. | Not explicitly required. |
| Forward/Proxy Detection | Gmail penalizes misaligned forwarding or proxy behavior. | No explicit guidance provided. |
| From: Header Alignment | Must align with DKIM/DMARC domain. | Recommended |
| Inactive/Invalid User Management | Indirectly enforced through spam rate and complaint thresholds. | Recommended |
| Functional Reply-To Address | Recommended | Recommended |
| Transparency (Subject lines, headers) | Recommended to avoid misleading info. | Recommended to avoid misleading info. |
| Timeline for Enforcement | Full enforcement began February 2024. | Enforcement begins May 5, 2025 with rejections at a later TBD. |