> If you are invovled in developing, supporting, or maintaining an application that sends emails, this guide is a must read.
I would also say a guide like this is helpful whenever you are using a custom domain with an email service, and therefore need to set these records yourself. Okay, you might not need to have an in-depth knowledge of these concepts, but it's certainly helpful to understand why your email provider is telling you to set all these weird DNS records.