Opt-in (or Subscribe)
Opt-in is the act of giving consent to receive marketing emails, typically by subscribing via a form or checkbox.
Opt-in, also called subscribing, is the action by which a person gives a business permission to send them marketing email. It is usually collected through a signup form, a checkbox at checkout, or another step the person takes on purpose.
Send marketing campaigns only to people who opted in. The record of that choice is also your evidence if a recipient, mailbox provider, or regulator asks why someone is on your list.
Opt-in and the law
Consent rules differ by country. In Canada, CASL generally requires express or implied consent before sending a commercial electronic message, with limited exemptions, and the sender carries the burden of proving that consent. Express consent must come through an opt-in step such as signing up on your website, and it does not expire until the person withdraws it. The CRTC’s guidance on implied consent describes both forms.
The US CAN-SPAM Act works differently. It does not require prior consent for commercial email, but every commercial message must include a working opt-out, and the sender must honor an opt-out request within 10 business days. See the FTC’s CAN-SPAM compliance guide. Other jurisdictions have their own rules, so check the ones that apply to your recipients.
Single vs double opt-in
Single opt-in adds the subscriber as soon as they submit the form. Double opt-in sends a confirmation email first and adds the subscriber only after they click it. Keep the signup wording and consent record with either approach.
Common mistakes
Pre-checked boxes, consent buried in terms of service, and importing addresses collected for another purpose. Each produces a list of people who never chose to hear from you, and none produces a record you can point to later.