Express consent is permission for something that is given specifically, either verbally or in writing.
Express consent contrasts with implied consent, which is an assumption of permission that is inferred from actions on the part of the individual. The terms are often heard in relation to email marketing campaigns and anti-spam legislation. Express consent is generally valued more highly than implied consent, and marketers are often less restricted when email recipients have opted-in to receive their mailings.
Best practices for email marketing include asking recipients specifically to consent to mailings and requiring double opt-in procedures (such as replying to an email or signing up online and also clicking a follow-up link to confirm). Marketers should provide the name of the party requesting permission and the company's name, address website, phone number and physical / postal addresses. It's also crucial to included a functional unsubscribe link.