Even in 2011 I heard that email marketing was dead. Yet I saw an advantage social networks did not offer: a person could choose to receive messages from you in their inbox. An email list is therefore more than a collection of addresses. It is an agreement about the information you will send.
Give people a reason to join
“Sign up for our newsletter” says very little. Readers want to know what they will receive and how often. In my old article I suggested offering a free ebook. That can work if the guide answers a real question and fits the later emails. A giveaway unrelated to your newsletter mainly attracts people who leave after the download.
For example, an adviser who writes practical articles for entrepreneurs might offer a short checklist, then send new examples from time to time. At signup, make clear that receiving the guide and receiving later emails are distinct things. Ask permission for the messages you plan to send and make leaving easy.
Begin the relationship well
A first message can deliver the promised download and explain what comes next. It does not need to be followed immediately by a sales pitch. A short sequence with useful answers can show what you know. In my old article I called this an autoresponder; the principle remains that new readers receive the most important information in a sensible order.
Do not measure only how many addresses a form collects. See whether readers open, click, reply and stay subscribed. Adjust if your promise and your emails drift apart. The value of a mailing list ultimately lies in trust that you earn again with each message.