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.
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.