Gmail and Yahoo’s email sender requirements, explained

Who the rules apply to

Google defines a bulk sender as anyone sending more than about 5,000 messages a day to personal Gmail addresses. Yahoo’s rules apply to bulk senders as well. If you cross that line once, Google treats you as a bulk sender from then on.

Below that threshold the strictest rules are not enforced the same way, but every sender is expected to have SPF or DKIM, and mail with no authentication is far more likely to be rejected or sent to spam. In practice you should meet all of them.

What is required

• Authenticate your mail. SPF and DKIM for the domain you send from. See SPF and DKIM.
• Publish a DMARC record. At minimum p=none, and the From domain must align with SPF or DKIM. See DMARC.
• One-click unsubscribe on marketing and subscribed mail: the List-Unsubscribe and List-Unsubscribe-Post headers, plus a visible link in the body. Unsubscribes should be honoured within two days.
• Keep spam complaints low. Google asks for a spam rate under 0.10% in Postmaster Tools and says never to reach 0.30%.
• Send over TLS, and make sure the servers you send from have valid forward and reverse DNS.
• Format messages properly and do not impersonate Gmail’s own From addresses.

Transactional mail is treated differently, up to a point

The one-click unsubscribe rule is for marketing and subscribed mail. A password reset or a receipt does not need an unsubscribe link, and should not have one. Authentication, DMARC and a low complaint rate apply to everything you send from the domain.

How to check where you stand

1. Check your domain’s SPF, DKIM and DMARC. Run your domain through the free domain checker to see it.
2. Register the domain in Google Postmaster Tools. It shows your domain’s reputation and spam rate once you send enough mail for it to have data.
3. If you send newsletters, check that each one has the unsubscribe header and a working link. SendSend adds both to every broadcast automatically.