Sign-up and double opt-in

Double opt-in means a new contact is created as pending and receives one email asking them to confirm. Until they click, they are subscribed to nothing and receive nothing else. Switched off, a contact added through the API is subscribed straight away.

Why it is a floor

The setting lives with the organization, and an API call cannot turn it off. A script that adds contacts can ask for double opt-in when the organization does not require it, but it can never skip it when the organization does. That is what makes it worth anything. A consent rule a caller can waive is not a rule.

The confirmation email is yours

It is a real template, edited on the sign-up screen — subject and full HTML, with a live preview and a test send, exactly like a template. It starts from a default content; edit it and it becomes yours, and you can restore the default at any time.
{{confirmationUrl}} is mandatory. Without it the recipient has no way to confirm and stays pending forever, so saving is refused. It is the one variable this email cannot do without.
This email is not a marketing email: it has no unsubscribe link, because the recipient is not a subscriber yet. It is also not part of your template library and never appears there — an organization has one, not a collection.

What it changes for consent

Confirming records the date and the IP of the click, next to the date and IP of the original sign-up. Those four fields are the proof you would produce if anyone asked, and nothing but a real sign-up and a real click can write them. An import never triggers a confirmation email, whatever the setting: it carries the proof columns from the export instead.

What refuses

The test send goes through the real sending path, so it fails for the same reasons a campaign would: sending paused across AgentsMail, organization not allowed, domain not verified. See why a send is refused.

What it implies elsewhere

A pending contact counts against your plan's contact ceiling — they exist, they are just not subscribed. They never appear in a campaign audience, and no segment can reach them. The settings and the confirmation email are both reachable over HTTP: see Settings & domains.