MailCatcher runs a super simple SMTP server

I don't understand. What are use cases for using this or Mailpit? Can't you just create a new email address on existing server and check it? Why do you need different setup and different infra?

This is useful for non prod environments, especially local, where you don’t want some background job sending emails welcome to jdoe@gmail.com when you are testing the sign up flow. It allows you to safely send outbound emails to any address without worry that they will actually be delivered, without having to change your application code.

Local development of an app that will send email. For example, when I'm building a django app, running it via `runserver`, I don't want it to go to an external mail server. And using the console logger for SMTP gets really noisy. Being able to point my browser at Mailpit's web UI lets me see all the messages the app has sent.

It's particularly nice for things like magic links and testing that email confirmations are working.