There are several email marketing providers available, such as Mailchimp, Constant Contact, and Campaign Monitor. Each provider has its own set of features and pricing plans, so it's essential to choose one that fits your budget and requirements.

Once you have done this please integrate the email marketing provider with your app. To do this refer to this article

While the integration is happening you can write out your emails. The design of your newsletter is crucial in catching the attention of your subscribers. Keep the design clean and simple, with a clear call-to-action that directs users to your app. Use eye-catching images and graphics to make your newsletter visually appealing.

Along with automated emails, the content of your newsletter should be informative and engaging. You can include updates on new app features, exclusive content, and special promotions. Make sure to tailor your content to your target audience.

Once you've designed your newsletter and chosen your content, it's time to schedule your emails. The emails should be triggered based on the subscribers receiving certain tags. For example, when a user gets a "register" tag you should send them an automated welcome email and or a series of emails welcoming them to the app! The frequency of your emails will depend on your app and target audience, but generally, sending one email per week is a good starting point.

After sending out your newsletters, it's important to analyze your results. Look at open rates, click-through rates, and unsubscribe rates to determine the effectiveness of your email campaign. Use this data to refine your strategy and improve engagement with your subscribers.

In conclusion, email marketing is a powerful tool for retaining users in a subscription app. By following these six steps, you can set up an effective email newsletter that keeps your users engaged and informed about your app.