Article · 6 min read

Strengthening email security: Outlook's new requirements for high-volume senders

Puneeth · Microsoft Tech Community (Outlook blog) Free Intermediate

Microsoft's own announcement of the sender rules for Outlook.com, Hotmail and Live addresses, which made Microsoft the third of the big mailbox providers, after Gmail and Yahoo, to require authentication from bulk senders.

  • Applies to domains sending more than 5,000 emails a day to Outlook.com, Hotmail and Live addresses.
  • SPF and DKIM must pass, and DMARC needs at least a p=none policy aligned with SPF or DKIM, preferably both.
  • Enforcement began on 5 May 2025, with non-compliant mail first routed to Junk and rejection to follow, and the Safe Senders list does not bypass it.
  • Also recommends a visible unsubscribe link, regular removal of invalid addresses, and mailing only people who consented.
Open on techcommunity.microsoft.com ↗

It answers 2 questions

  1. Should I let an AI SDR send our cold email, and how do I stop it burning our domain?
  2. We send a newsletter and product email to thousands of people. What do Gmail, Yahoo and Microsoft now require from us?

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