It's best practice to always use double opt-in for your subscription forms. Double opt-in means that after your visitor initially enters their email address to subscribe to your list, BoltMail will then send them a "confirmation" email. This email contains a special link which will then verify that this visitor did indeed sign up to your mailing list.
This is very important because many people can accidentally enter an incorrect email address, or even the email address of someone else on purpose. When that person receives a newsletter they did not subscribe to, they will assume they have been spammed, and your newsletter will be reported as spam.
It is also common for subscription and contact forms to receive automated spam submissions from bots, these submissions will often use email addresses scraped from other websites. These scraped addresses wont be expecting to receive emails from you and worse some of them could be spam traps or honey pots. Using double opt in is effective at screening out out these automated submissions thus keeping your list clean. Learn more about The dangers of spam traps and honey pots
To enable double op-in, when creating a new list, or when editing the settings of an existing list, find the "Opt in" box and choose "Double opt-in".
If you are using a list purchased from a third party or an old list that you haven't sent marketing emails to before, it is essential that you re-confirm all the subscribers. See Reconfirming your subscribers
