No, you should stick with a single opt-in for your email popup. Adding a confirmation step (double opt-in) creates friction that will noticeably shrink the number of people who actually join your list, which defeats the point of the popup in the first place.
The whole game with popups is to make signing up as easy as possible. On Ecommerce Coffee Break, Soma Toth talked about the power of "one-click opt-ins" because customers hate extra steps and typing. Your goal is to capture the email with minimal effort from the user. Requiring them to go to their inbox and click a confirmation link is a major hurdle, and you'll lose a lot of legitimate, interested subscribers who simply don't complete that second step. This hurts your ability to grow your list quickly.
The only real reason to consider double opt-in is for list hygiene and improved email deliverability. On another episode of the same show, host Claus Lauter made the point that double opt-in ensures you're getting real, confirmed email addresses, which weeds out typos or people using fake emails just to get a discount code. This leads to a smaller, but potentially more engaged, list. For most stores, however, the faster growth from a single opt-in is far more valuable. You can always clean your list later.
