Mobile App Growth Hacks: Build a Mailing List

In this post I’m going to write about a growth hack that my team uses for one of our apps - Wind Tracker. Many mobile apps require some form of registration, whether through social media profiles or email. Most apps only use the profile information to authenticate the user. However, there are some other smart things that app developers can do in order to increase engagement and collect valuable feedback. Emails are not the obvious way to do this, but the truth is that many successful apps use them effectively as I’ll show below.

In our case we use Firebase Authentication to manage the sign-in process. It’s completely free! You can select from several sign-in methods - Email/Password, Google, Facebook, Twitter, Github, Phone or Anonymous. We provide three methods - Facebook, Google (the most popular ones) or Anonymous. While the first two methods allow you to access the primary email of the user, the third one, Anonymous, is a kind of good practice. Some people won’t give you access to their private information for free, you need to gain their trust.

1. Build a mailing list

If you want to properly connect with your users you need a channel for communication. There are plenty of options like push notifications, chat bots or social media, but emails are the oldest and most popular one. There is nothing wrong with having a mailing list for your users as long as they receive relevant content at the right time. Mailing lists usually contain name and email but depending on the information collected by the app, they may contain additional information; interests, location, language, gender, etc. Also there can be one list for normal users, one for purchasers, one for power users and so on. Having those additional properties can be really helpful when narrowing down large groups, making it easier to send users relevant content.

Our recommendation is to use MailChimp to build a mailing list. MailChimp not only has a free quota of 2000 users, but it also has a very powerful API. There are no limitations to access the API, you only have to obtain a key. But wait … how do you access the API? That’s a good question. Since we used Firebase for authentication, we decided to use Firebase Cloud Functions as a backend. All you need to have is some knowledge of Javascript/Node.js or know a programmer who can help you. To see how simple the code is, you can take a look at this article.

2. Send automated welcome email

You’ve probably received welcome emails many times before. For example, here is a welcome email that I received after I registered and purchased a membership in the mobile app Audible.


You may ask, why do I need to send welcome emails to my users? Well, there are several reasons to do so. First of all, it’s not just a simple email, it sets the tone for how you will be communicating with your list. It will deliver the first impression and most importantly, communicate what people can expect from the app. Secondly, it keeps the audience engaged. The welcome email provides a way to speak to your users and keeps your app top of mind within your category. Third, it offers a chance to capitalize on sales. When a new user registers in your app, that’s a signal that they are ready to learn more about the benefits you provide. Take that chance and capitalize on the opportunity. If you have in-app products, this is the perfect moment to offer them. Last but not least, it helps you to build trust. How? A warm welcome message and introducing yourself. Even though the user may already know you, it is a big step in building rapport. You can tell them who you are, what your values are, and why they should choose your app over the competitors.

Once you start automatically adding new users directly into your mailing list, sending an automated welcome email with MailChimp is a straightforward task. You can just follow the official article.

3. Keep in touch with your users

Sometimes people forget about your product. Don’t take it personal; it’s not because you provide a bad service, they are probably just busy. By using an automatically triggered email you can remind them about your product or a promotion. Below you’ll see how Spotify reminded me about their promotion.


Another great way to keep in touch with users is by sending them activity emails or digest emails. The first type, also known as transactional emails, are sent when something important happens in the app. For example, AirBnB sent me a reminder about an upcoming trip.

AirBnB - reservation

The email includes everything you need to know - address, dates, receipt, reservation code and phone number of your host. It’s amazing that you can reference all this from the email instead of having log back into the app. Very useful!

Digest emails are a great way to engage your users with regular communication. They have become a key feature of products like YouTube and Twitter. I’m not going to go into details, I’ll just mention that digest emails are a great way to summarize user activity, show analytics or engage users with personalized content from your app. Toggl, a popular app for time tracking, sends weekly emails with an overview of your tracked time.


MailChimp makes it easy to design and create emails which are triggered at a certain time for a specific target group. There are different types of triggers you can choose from, but you’ll most probably use 'list added date', i.e. the time when the user has subscribed to your list. On the other hand, segments will give you the power to target a smaller audience. Segments are basically filters applied to your list. You can filter by list fields or groups. In Wind Tracker we have segments of users with certain interests like windsurfing and paragliding. It allows us to send them relevant content - windsurfers will be interested in content related to water sports while paragliders will be interested in content related to air sports.

4. Collect feedback

Understanding your users is pivotal to having a successful mobile app. You can use Google Analytics for Firebase or a similar analytics tool that provides insight on app usage and user engagement. Unfortunately such kind of analytics don’t give you the full picture, they only show you the surface. You need to dig deeper and look beyond the basic metrics like average session time and demographics. How? One simple way is to just ask your users - “Why do you use my app? What’s the most valuable feature for you?” or “Why did you uninstall my app? What’s your recommendation to improve the service?”.

If someone keeps our app, Wind Tracker, for two days on their device, we’ll send an email asking them to fill out a survey with one question - “Why know the wind conditions?” Timing is crucial for this kind of emails, you may need to do some A/B testing in order to figure out the best time to send the survey.


In case someone removes our app, they will receive a similar email asking them to fill out another survey, again, with one question - “What made you uninstall?” My advice is to send this email as soon as the user gets rid of your app. You want to catch them when they are most disappointed and probably going to be most critical of you. But that’s ok, it’s the only way to understand what people really think about your app 🙂