We recently had occasion to write down in great deal the exact definitions of the various levels of opt-in when it comes to building email marketing lists or other types of email lists. Because there is some confusion on this, especially where one method of list-building may have more than one name, we thought that we'd share these descriptions and definitions of Confirmed Opt In (COI), Double Opt In, Single Opt In, Opt In, Transactional, and One to One (1 to 1) email with you.
