To meet the legal requirements of countries with double opt-in laws (such as Germany), a specific, multi-step process must be implemented. This involves a person first submitting their information via a form and then confirming their subscription by clicking a unique link in a follow-up email. In Marketo Engage, this is accomplished by creating a set of processes, typically involving two smart campaigns: one to send the confirmation email upon form submission, and a second to listen for the confirmation link click, which then officially opts the person into marketing communications. This entire workflow constitutes the "processes" required for compliance.

A. Include an Unsubscribe link in all marketing emails

This is a requirement for opting out under laws like CAN-SPAM and GDPR, but it does not address the initial, two-step confirmation process required for double opt-in.

B. Add a checkbox with verbiage stating that by filling out the form, the lead consents to receive email

This action establishes single opt-in (explicit consent), but it lacks the second verification step (clicking a confirmation link) that defines and is required by double opt-in laws.

C. Suppress all non-US respondents

This is a business strategy to avoid the compliance challenge altogether, not a solution to meet the legal requirements for the leads you wish to engage.

1. Adobe Experience League, Marketo Engage Documentation, "Set up a Double Opt-in Process." This official guide details the necessary steps, which involve creating two distinct smart campaigns. It states, "Double opt-in is when a user subscribes to a mailing list and then receives a confirmation email with a link they must click to confirm their subscription." The entire procedure described is a "process," confirming that option D is the correct high-level action required.

2. Adobe Experience League, Marketo Engage Documentation, "GDPR and Marketo Engage." In the section on "Consent," the documentation emphasizes the need for systems to manage and record consent. It notes that for jurisdictions requiring it, "Marketo Engage can be configured to support a double opt-in process." This configuration is precisely the creation of processes mentioned in option D.