What is the List-Unsubscribe header?

The List-Unsubscribe header provides a standardized way for recipients to unsubscribe without hunting through email content. Email clients parse this header to display unsubscribe options in their interface.

RFC 2369 defines List-Unsubscribe with two mechanism types:

HTTPS URL: List-Unsubscribe: <https://example.com/unsubscribe?id=abc123>

Mailto address: List-Unsubscribe: <mailto:unsubscribe@example.com?subject=unsubscribe-abc123>

Both can be included: List-Unsubscribe: <https://...>, <mailto:...>

List-Unsubscribe-Post enables one-click functionality:

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

This tells clients they can POST to the URL without user confirmation, enabling true one-click unsubscribe.

2024 Gmail and Yahoo requirements mandate both headers for bulk senders (5,000+ daily messages). The unsubscribe must be honored within two days.

Benefits:

Easier unsubscribe reduces spam complaints

Prominent client UI placement

Shows sender transparency and legitimacy

Required for compliance with major providers

ESPs typically add these headers automatically. Verify they're present and functional.