We've been using letter_opener (https://github.com/ryanb/letter_opener https://github.com/ryanb/letter_opener), which handles the "preview" case very well (open

We've been using letter_opener (https://github.com/ryanb/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.