Someone voluntarily gives you their email address either online or in person so you can send them emails. They may pick certain types of email content they wish to receive, like specifically requesting email alerts when new blog posts are published. Opt-in email addresses are the result of earning the interest and trust of your contacts because they think you have something valuable to say.
Julie Ewald recommends moving away from sending generic content to your whole email list via e-blast entirely. With a little elbow grease, you can utilize segmentation and start sending off tailored messages to each of your lists with content that’s relevant, valuable, and designed to resonate with the kind of recipients that make up each segment.