When mail is sent from your application, Letter Opener will open a preview in the browser instead of sending.

MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a web interface. Run mailcatcher, set your favourite app to deliver to smtp://127.0.0.1:1025 instead of your default SMTP server, then check out http://127.0.0.1:1080 to see the mail.

Visual email testing

A Rails Engine to preview plain text and html email in your browser

Email Condom for your Ruby Server. In Rails, Sinatra, et al, or simply the mail gem: Aids in development, testing, qa, and production troubleshooting of email issues without worrying that emails will get sent to actual live addresses.

A mock SMTP/POP3 server to aid in the development of applications with mail functionality.

An Action Mailer delivery method that opens emails locally.