Graymail

What it means

Microsoft's documentation says messages from a bulk sender are known as bulk mail or gray mail. Good bulk senders send wanted messages with relevant content to subscribers and draw few complaints; others send unsolicited messages that closely resemble spam and draw many. Microsoft rates each with a bulk complaint level and treats mail at or above the policy threshold as bulk, delivering it to the Junk Email folder by default.

Graymail sits between clear spam and wanted mail, so the same newsletter can be welcome to one recipient and junk to another. For senders, the levers are the ones that lower complaints: confirmed opt-in, clear expectations at signup, honest frequency and an easy unsubscribe.