AWeber is pretty close-lipped about their security measures; while there is a very short section on security in the company’s privacy policy inviting readers to contact the company for details, I did precisely that and was simply told they couldn’t discuss security measures for security reasons. (I find the argument unconvincing, given the basic security information freely available on competitors’ sites.)
Like I said, most ESP (email service providers) have the capability of creating automated email workflows. So, instead of getting an email subscriber and initially sending them one or two emails, before getting distracted and forgetting all about them, you can be sure that you have emails sent to them over the course of a few days, weeks, months etc. with email automation.
Email marketing is such a critical component of business for most companies (with the rare exception) because you able to communicate with your audience in the place they spend a good chunk of time (their inboxes). You also have the added benefit of building an asset (an email list) that no external platform (I’m talking to you Facebook) can mess with.

Using the Personalize dropdown, you can insert custom snippets like your subscribers first name, or sign up date, and AWeber will automatically insert that data specific to each subscriber if we have it. If you collect first name, for example, you can send an email that says Hello Tom, or Hello Mary, or Hello John, depending upon who you’re sending to.