High spam score: MISSING_LIST_HEADERS

Your bulk/newsletter email is missing List-Unsubscribe and List-ID headers. Receivers treat it as unsolicited bulk mail.

Impact — Medium impact

As of Feb 2024, Gmail and Yahoo REQUIRE List-Unsubscribe for bulk senders (>5000/day). Without it, you'll see bounces, spam folder placement, and eventual full blocking.

What causes it

You're sending bulk mail through a service that doesn't automatically add list headers.
You're sending from your own app code without constructing these headers.
Your mail template or MIME construction omits them.

How to fix it

Step 1: Add List-Unsubscribe header

Minimum: List-Unsubscribe: , . Both methods required.

Step 2: Add List-Unsubscribe-Post for one-click

Gmail now requires one-click unsubscribe. Add: List-Unsubscribe-Post: List-Unsubscribe=One-Click. Your /unsubscribe endpoint must accept POST requests and process without further confirmation.

Step 3: Add List-ID

Format: List-ID: "Your List Name" . This helps receivers categorize and group messages correctly.

Fixed it? Run a fresh test to confirm.

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