Gmail sender requirements, plus Yahoo and Outlook.com rules

Changelog: what changed and when

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The latest changes at Gmail, Yahoo, Microsoft and Apple, month by month, are in our deliverability news.

Gmail sender requirements at a glance

Google’s email sender guidelines split the rules into two levels. Bulk senders have to meet everything in the “All senders” column too.

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Details that trip people up:

• The PTR record has to match. Google: the sending IP “must have a corresponding PTR record that resolves to a hostname”, and that hostname must resolve back to the same IP.

• 0.3% is the limit, not the goal. Google recommends keeping the spam rate “below 0.10%” and never reaching 0.30%.

• One-click unsubscribe means two headers (RFC 8058):

  List-Unsubscribe: <https://example.com/unsubscribe/opaque-token>
  List-Unsubscribe-Post: List-Unsubscribe=One-Click
  

• The headers don’t replace the link. Marketing messages also need a clearly visible unsubscribe link in the body.

To set up the records, see SPF record, DKIM record and what is a DMARC record, or create a DMARC record with the DMARC record generator.

Who counts as a Gmail bulk sender

Google’s sender guidelines FAQ defines a bulk sender as one that “sends close to 5,000 messages or more to personal Gmail accounts within a 24-hour period”. Three details matter:

• Messages from the same primary domain count together, so news.example.com and mail.example.com add up.
• “Senders who meet the above criteria at least once are permanently considered bulk senders.”
• The guidelines “don’t apply to messages sent to Google Workspace accounts”. Only personal Gmail recipients count.

Gmail bulk sender requirements: enforcement from 2024 to 2026

The requirements haven’t changed since February 2024; enforcement has. Google’s FAQ says that “starting November 2025, Gmail is ramping up its enforcement on non-compliant traffic”, and that non-compliant messages “will experience disruptions, including temporary and permanent rejections.”

What that looks like in practice:

• Authentication failures: messages “might be marked as spam or rejected with a 5.7.26 error” (what 550 5.7.26 means).
• Temporary failures: Google sends 4.7.x codes for authentication, TLS and PTR problems, which your server retries (421 explained).
• Unsubscribe problems: Gmail doesn’t automatically reject these messages or send them to spam, but bulk senders without working unsubscribe aren’t eligible for mitigation.

Google Postmaster Tools has a compliance status dashboard that shows, for your domain, whether you meet each requirement: SPF and DKIM, DNS records, message formatting, encryption and spam rate for everyone, plus DMARC, one-click unsubscribe and honoring unsubscribes for bulk senders.

Yahoo sender requirements

Yahoo’s Sender Hub lists almost the same rules. Enforcement began in February 2024.

All senders:

• SPF or DKIM at a minimum.
• A spam rate below 0.3%.
• Valid forward and reverse DNS for sending IPs.
• Mail that complies with RFC 5321 and RFC 5322.

Bulk senders, in addition:

• SPF and DKIM, and a DMARC policy of at least p=none that passes. Relaxed alignment is fine; the From domain must align with the SPF or the DKIM domain.
• A working List-Unsubscribe header with one-click unsubscribe for marketing and subscribed messages, plus a visible unsubscribe link in the body. Yahoo accepts the mailto: method and “highly recommends” the RFC 8058 POST method.
• Honor unsubscribes within 2 days.

Three differences from Gmail: Yahoo doesn’t publish a number of messages that makes you a bulk sender, its requirements list doesn’t mention TLS, and it calculates the spam rate on mail delivered to the inbox.

Outlook.com requirements for high-volume senders

Microsoft announced rules for high-volume senders in April 2025 on its Tech Community blog. The binding text is in the Outlook.com postmaster policies:

• Who: domains sending more than 5,000 emails a day to Outlook.com accounts.
• Since when: “Effective May 5th, 2025”.
• What: SPF, DKIM and DMARC, all in place. DMARC at least p=none (Microsoft recommends p=reject), aligned with SPF or DKIM, ideally both.
• Enforcement: non-compliant messages from high-volume senders go to the junk folder. If the problems aren’t fixed, Outlook.com may reject them with:

550; 5.7.515 Access denied, sending domain [SendingDomain] does not meet the required authentication level.

For all senders, the policies require an unsubscribe mechanism that is “clearly documented and easy for recipients to find and use”, say a sender must stop sending to a recipient after multiple non-delivery responses, and point to two free Microsoft services for managing your reputation: the Junk Email Reporting Program (JMRP) and Smart Network Data Services (SNDS).

Gmail, Yahoo and Outlook.com side by side

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Checklist

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Meeting the requirements gets you accepted; it doesn’t get you into the inbox on its own. The email deliverability guide covers reputation, list quality and content.

Sources

All checked October 9, 2026:

• Google: Email sender guidelines, Email sender guidelines FAQ, Postmaster Tools dashboards
• Yahoo: Sender Hub best practices
• Microsoft: Outlook.com postmaster policies, practices and guidelines, announcement on Microsoft Tech Community
• RFC 8058: signaling one-click functionality for list email headers