[jbredeche]

We've been using letter_opener (https://github.com/ryanb/letter_opener), which handles the "preview" case very well (opens the rich text and plain emails in separate browser tabs on send). Doesn't do the other stuff that mails_viewer does, but a good lightweight alternative.

[cmer]

Another alternative is Mail Catcher which we've been using with much success. http://mailcatcher.me/