Many email senders are reluctant to move existings lists to a confirmed opt-in (sometimes called "double opt-in") model for fear of losing many of their existing users, and reducing the size of their mailing lists. When called upon to confirm or reconfirm a mailing list - say, for example, when moving their mailing list to a new email service provider (ESP) - they balk, and will even go to a second tier ESP that doesn't require reconfirmation. The reason is always the same: "We don't want to lose a portion of our users." But what these senders overlook is that they actually will improve - sometimes dramatically improve - the responsiveness of their mailing lists - and the financial return that they receive from those lists. In fact, we have the email deliverability white paper to prove it.
