Do you send lots of emails with your Rails app, and wish you had a way to spot check them? Fix those typos, and make sure the dynamic content looks correct? It’s easy to verify there are no code bugs with Rail’s builtin Mailer preview. But how do you prevent sending someone’s wrong order or personal information, especially if it’s in a batch of emails? You need to generate those emails, and make sure they match everything. https://onrails.blog/2020/10/12/introducing-mailbox-tester/