What are “List-Unsubscribe” headers?

List-Unsubscribe headers tell email clients how to unsubscribe recipients without requiring them to find and click links in the message body. They enable "one-click" unsubscribe buttons in clients like Gmail.

There are two related headers:

List-Unsubscribe: Contains URLs or mailto addresses for unsubscribing.

List-Unsubscribe: <https://example.com/unsubscribe?id=abc123>, <mailto:unsubscribe@example.com?subject=unsubscribe>

List-Unsubscribe-Post: Enables one-click unsubscribe via HTTP POST. Required for true one-click functionality.

List-Unsubscribe-Post: List-Unsubscribe=One-Click

The Gmail and Yahoo 2024 requirements mandate both headers for bulk senders sending over 5,000 messages daily. The unsubscribe must complete within two days.

Benefits:

Recipients can unsubscribe easily, reducing spam complaints

Prominent unsubscribe options in the email client interface

Demonstrates sender transparency and legitimacy

ESPs typically add these headers automatically. If self-hosting, configure your MTA or application to include them.

It's posting your port of exit clearly. Passengers can disembark easily rather than jumping overboard and filing complaints.