I have a client that has amassed a lot of their customer emails in the past year, written with a pen on paper. I'm not completely familiar with email marketing, but am getting into it, but from what I understand, you should do a double opt-in to comply with Can-Spam laws, is that correct? Is there a way to use one of the popular email marketing sites (Aweber, Mailchimp, ImnicaMail) and manually enter their customer's emails so that they can start sending a newsletter to them right away? Or do they have to opt in (either single or double), even though they already gave the company their email address in the past? Thanks the for the input.