Sending

Unsubscribe links

A `POST /emails` send carries an opt-out only when it sets `topic_id`; campaigns inject a per-contact unsubscribe link and List-Unsubscribe header automatically.

How unsubscribe is handled depends on what you are sending: a transactional email, a topic email (POST /emails with topic_id), or a campaign.

Send	Unsubscribe footer + `List-Unsubscribe`	What an opt-out does
`POST /emails` without `topic_id`	No — never added	—
`POST /emails` with `topic_id`	Yes — added automatically	Removes that address from that one topic
Campaign	Yes — added automatically	Unsubscribes the contact from all your email

Transactional emails (sender-driven)

For POST /emails without a topic_id, MailBlastr does not add an unsubscribe link or List-Unsubscribe header. Transactional sends — receipts, password resets, confirmations — are sender-driven: if a message needs an unsubscribe mechanism, you add it to your own HTML. This keeps MailBlastr from injecting footers into messages where they don't belong.

This is deliberate, not an omission. In MailBlastr an unsubscribe writes a suppression, and a suppressed address is skipped by every later send to it — password resets and receipts included. A footer on a password-reset email would let one stray click permanently break that recipient's own account recovery. Mark a send as subscription mail with topic_id and you get an opt-out that is scoped to the topic instead.

If a recipient should be able to opt out of a transactional email, include your own unsubscribe link in the html body. You can record the resulting opt-out as a suppression so future sends to that address are skipped.

If you manage your own list and want a native one-click control on transactional mail, you can set the headers yourself via the `headers` object — a List-Unsubscribe header pointing at your unsubscribe URL, plus List-Unsubscribe-Post: List-Unsubscribe=One-Click for RFC 8058 one-click support.

"headers": {
  "List-Unsubscribe": "<https://example.com/unsubscribe>",
  "List-Unsubscribe-Post": "List-Unsubscribe=One-Click"
}

When honoring a one-click request, your endpoint should accept a POST from that URL and return a blank 200 OK or 202 Accepted (and serve the normal unsubscribe page on GET). Ensure the recipient stops receiving email within 48 hours. Mailbox providers such as Gmail and Yahoo require RFC 8058 compliance for bulk senders (more than 5,000 messages per day to their domains).

Topic emails (automatic, scoped to the topic)

A POST /emails send that sets `topic_id` is subscription mail: MailBlastr already skips recipients who have left that topic, so it also gives every recipient a way to leave. Both mechanisms are added automatically, exactly as they are for a campaign:

An unsubscribe footer appended to the HTML body — unless your body already contains a MailBlastr unsubscribe link (see the merge tag below), in which case yours is left alone.
An RFC 8058 `List-Unsubscribe` header with `List-Unsubscribe-Post`, so mailbox providers can render their native one-click unsubscribe control.

The link is minted per recipient from that recipient's own address, so every to, cc, and bcc address is delivered its own copy carrying only its own opt-out link — one recipient can never opt out another. The recipient does not have to be a contact: the opt-out is recorded against the address itself.

The scope of the opt-out is that one topic. It is not a suppression and not an audience-wide unsubscribe: the address keeps receiving your other topics, your campaigns, and your transactional mail. Only later sends carrying the same topic_id — from POST /emails, a scheduled send, or a campaign targeting that topic — skip it.

To place the link yourself instead of taking the default footer, include {{{MAILBLASTR_UNSUBSCRIBE_URL}}} in your html (triple braces so the URL is inserted raw). MailBlastr substitutes each recipient's own URL and then skips the default footer, so you get one opt-out link, where you put it — not two.

Topic opt-outs are listed per topic in the dashboard under Audiences → Topics → View opt-outs, showing both contacts who opted out and addresses that used a topic unsubscribe link.

Campaigns (automatic)

For campaigns (marketing email to an audience), MailBlastr injects unsubscribe handling automatically for every recipient:

A per-contact unsubscribe link is appended to the message footer. Each recipient gets a unique link, so one click opts that individual out.
An RFC 8058 `List-Unsubscribe` header (with List-Unsubscribe-Post) is emitted so mailbox providers can render a native one-click unsubscribe control.

When a contact unsubscribes through either path, they are added to your suppression list and skipped on subsequent sends. The unsubscribe link is appended after any click-tracking rewrite, so the opt-out link is never wrapped by the click tracker.

Don't set a List-Unsubscribe header by hand on a campaign — MailBlastr manages it. See Custom headers for transactional header usage.