In February 2024 Gmail and Yahoo started enforcing stricter rules for anyone sending to their users. Some apply to every sender; the strictest apply to bulk senders — Google defines these as sending close to 5,000 or more messages a day to personal Gmail accounts.
Requirements for all senders
- Set up SPF or DKIM for your sending domain
- Valid forward and reverse DNS (PTR) for sending IPs
- Use a TLS connection when sending
- Keep the spam rate reported in Postmaster Tools below 0.3%
- Format messages according to RFC 5322
- Do not impersonate Gmail From addresses
Additional requirements for bulk senders
- Set up both SPF and DKIM
- Publish a DMARC record (at least
p=none) - The From domain must align with the SPF or DKIM domain
- Support one-click unsubscribe for marketing mail (List-Unsubscribe-Post header) and process requests within 2 days
- Include a clearly visible unsubscribe link in the message body
How to check your domain
- Run the Domain Checker for SPF, DKIM, DMARC and reverse DNS
- Send a test to a Gmail account and open Show original to see SPF, DKIM and DMARC results — or paste the headers into the Header Analyzer
- Register your domain in Google Postmaster Tools to watch spam rate
- Confirm your email platform adds one-click unsubscribe headers
Thresholds and enforcement details can change. Check Google's and Yahoo's sender guidelines for the latest wording.
Frequently asked questions
Do the rules apply if I send fewer than 5,000 emails a day?
The basic rules (SPF or DKIM, reverse DNS, TLS, low spam rate) apply to everyone; the DMARC, alignment and one-click unsubscribe rules target bulk senders.
What happens if I do not comply?
Messages may be rate-limited, sent to spam or rejected — often with 4.7.x or 5.7.26 errors.
Does Microsoft have similar rules?
Yes — since 2025 Outlook.com also expects SPF, DKIM and DMARC from high-volume senders.