Unsubscribe links
When an unsubscribe link is required, what a marketing send enforces, and why one-click unsubscribe means one recipient per message.
Marketing mail needs an unsubscribe mechanism and transactional mail does not; setting type: "marketing" is what tells Mailfully which gates to apply.
What a marketing send does for you
For a type: "marketing" send, Mailfully injects an RFC 8058 one-click unsubscribe URL into the message.
What a marketing send enforces
A marketing send is checked against three gates before it's accepted:
- Exactly one recipient across
to,cc, andbcc. - A postal address on file for the org.
- A separate monthly marketing allowance that has not run out.
Failing the recipient gate returns 422 marketing_single_recipient; failing the address gate returns 422 marketing_missing_postal_address; failing the allowance gate returns 429 marketing_quota_exceeded.
Why one recipient
A one-click unsubscribe URL identifies one person, so it can't be shared across recipients the way a shared to list works for transactional mail. A marketing send naming more than one recipient across to, cc, or bcc fails with 422 marketing_single_recipient.
Why a postal address
CAN-SPAM requires a physical postal address in commercial mail, so a marketing send with none on file for the org is refused with 422 marketing_missing_postal_address rather than sent without one. Add one in the dashboard; see CAN-SPAM.
A visible link in the body
A visible, working unsubscribe link in the message body is still expected of commercial mail. See Policies for the full compliance requirements, including the List-Unsubscribe and List-Unsubscribe-Post headers marketing messages must carry.
Transactional mail
Transactional mail needs no unsubscribe mechanism, and nothing requires you to add one to a genuinely transactional message. See Policies for where the line between the two categories sits.
Sending to someone who opted out
A marketing send to a recipient who opted out of marketing from your org fails outright with 422 recipient_unsubscribed. That's a different outcome from a send to a suppressed address, which is never rejected: see Why an address was suppressed for how bounces, complaints, and manual suppressions are instead handled silently.