Newsletters are sent once or twic times a month, using MailChimp. Subscriptions are done using a double opt-in system, so after you’ve filled in the subscribe form you get a confirmation email that requires you to click to confirm your subscription. If you don’t get it, do check it’s not stuck in your email spam filter. Mailchimp tracks newsletter opens and clicks, which I use to see what was the most popular reads. At the bottom of every newsletter is a link to unsubscribe or change your subscription details.