A List-ID on a solo ad is not an unsubscribe

Answer A List-ID header names the mailing list. It does not unsubscribe anyone. RFC 2919 defines that identifier. One-click unsubscribe is a different header. When a seller says the mail has list headers, ask which header, and look for the exit by its real name.

The note that started this: RFC 2919, List-Id: A Structured Field and Namespace for the Identification of Mailing Lists, RFC 2919.

The phrase list header sounds like compliance. It is often a label. A solo ad buyer who is learning the vocabulary will be shown a line that contains the word List and will be told the technical part is handled. The technical part that stops a complaint is the exit a person and a mailbox can both use.

RFC 2919 is from 2001. It specifies List-ID, a structured field and a namespace so software can tell one list from another. The value looks like a domain-shaped token, sometimes with a human phrase in front of it. Filters and mail clients can use it to group messages. Nothing in the act of naming the list removes a subscriber, writes a suppression, or satisfies a mailbox rule that wants a one-click POST. The name and the exit are different sentences. Sellers who blend them are counting on you not to notice.

What is a List-ID header?

It is a structured identifier for a mailing list, defined in RFC 2919. It names the list. It does not remove anyone from the list.

On a solo ad, the list is the seller's. A List-ID, if they publish one, should name that list, not the buyer's offer and not a fresh token invented for one drop. A stable identifier is a sign the mail is part of a continuing publication. A missing identifier is not, by itself, proof of spam. It is a sign you should ask what else is missing, because the exit is the part readers and mailbox providers actually use.

If you sell the send, pick a List-ID and keep it. Changing the identifier every time a buyer brings a new offer makes the mail look like a series of unrelated blasts that happen to share a from-name. The reader joined a list. Let the header say so. Then do the harder thing, which is the next section, and give them a way out that works.

• List-ID names the list the reader joined.
• The same identifier shows up on the seller's ordinary letters.
• The buyer's offer does not become the name of the list for one day.
• The identifier is never described as the opt-out.

Is List-ID the same as one-click unsubscribe?

No. One-click unsubscribe is a different header, the List-Unsubscribe and List-Unsubscribe-Post pair described in a later specification. A List-ID can be present on mail that still has no working exit.

List-Unsubscribe, specified long after RFC 2919, is the header that can carry a mailto or an https URL. One-click, in the modern mailbox rules, means a POST to that URL so the person can leave without logging in and without visiting a preference maze. A seller can have a perfect List-ID and a broken URL. A seller can have a visible line of tiny text that says unsubscribe and still fail the header a mailbox looks for. Ask for both. The body line is what a person reads. The header is what the mailbox button uses.

This is the practical half of safe solo ads sellers. The safe seller can show you the header from a recent send, not a diagram. You are looking for List-Unsubscribe, and for the POST if they claim one-click. You are not looking for a poetic list name. If they only have the name, say so in the quote, and decide whether that send belongs on a mailbox that expects the button.

What should a buyer ask for when a seller mentions list headers?

Ask to see List-Unsubscribe in a live header, ask whether a one-click POST is supported, and ask where the visible exit sits in the body. Accept a list name as a name, not as an opt-out.

Read the visible line yourself. It should say how to stop all marketing mail, in words an ordinary person can find. A link that leads to a checkout is not an exit. A link that leads to a page with twelve toggles and no stop-all is the menu problem from the CAN-SPAM note, wearing a different shirt.

Write the answer next to the from-name. Best solo ad vendors can show the exit before the invoice. A list identifier is a courtesy to software. The exit is the courtesy to the person who did not want this offer. Do not pay extra for a label that does not let them leave.