I have used tools like these for nearly a decade and find them invaluable. My current favourite is Mailpit [1].
The “OG” I would consider Mailcatcher [2] from my Rails days
The “OG” I would consider Mailcatcher [2] from my Rails days
An API driven approach like Msgdrop is more flexible, as many apps can’t configure a fake SMTP server, especially if you use tools like Mailgun or SendGrid.
[1] https://mailtrap.io.