Canada's Anti-Spam Legislation (CASL) is one of the strictest anti-spam laws in the world. CASL requires that you obtain explicit or implied consent before sending commercial electronic messages, including emails. Explicit consent means the recipient has clearly agreed to receive your emails, while implied consent may occur in the context of an existing business relationship. CASL also requires that each email includes the sender's contact information and a clear, easy, and free method for the recipient to unsubscribe.