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.