The key takeaways from this text are that early-stage companies need to architect their communication strategy carefully, as it can have significant second-order effects on product development iterations. Nodemailer is a popular project for sending emails in Node.js applications, and its success is due to its extensibility via plugins, security-first mindset, and ability to scale. The author of the text argues that buying over building non-core product features, such as communication strategy, can be a crucial trade-off for companies looking to grow faster. They also emphasize the importance of having multiple channels of communication, such as email, text messaging, and in-app messaging, to engage with users effectively. To address the complexity of choosing an email service provider, the author suggests using a layer of abstraction, such as Courier's API, to switch providers without rewriting code. The text concludes by highlighting the importance of writing and maintaining open-source projects that stand the test of time, such as Nodemailer, and providing a basic example of how to create a transport plugin for Courier in Node.js applications.