Single Opt-In eyepin Support Updated April 24, 2019 08:34 Follow Registration process, in which the single entering of an email address is enough to sign up for the newsletter. This procedure is legally questionable. Procedures such as confirmed or double opt-in are clearly preferable here. Related articles Double Opt-In What Opt-In Settings are there? Newsletter Opt-In A/B Split-Test Comments 0 comments Please sign in to leave a comment.