Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?


Failed to load latest commit information.


Build Status Gem Version Code Climate

Gives letter_opener an interface for browsing sent emails.

Check out to see it in action.


First add the gem to your development environment and run the bundle command to install it.

group :development do
  gem 'letter_opener_web', '~> 2.0'


Add to your routes.rb:

Your::Application.routes.draw do
  mount LetterOpenerWeb::Engine, at: "/letter_opener" if Rails.env.development?

And make sure you have :letter_opener delivery method configured for your app. Then visit http://localhost:3000/letter_opener after sending an email and have fun.

If you are running the app from a Vagrant machine or Docker container, you might want to skip letter_opener's launchy calls and avoid messages like these:

12:33:42 web.1  | Failure in opening /vagrant/tmp/letter_opener/1358825621_ba83a22/rich.html
with options {}: Unable to find a browser command. If this is unexpected, Please rerun with
environment variable LAUNCHY_DEBUG=true or the '-d' commandline option and file a bug at

In that case (or if you really just want to browse mails using the web interface and don't care about opening emails automatically), you can set :letter_opener_web as your delivery method on your config/environments/development.rb:

config.action_mailer.delivery_method = :letter_opener_web

If you're using :letter_opener_web as your delivery method, you can change the location of the letters by adding the following to an initializer (or in development.rb):

LetterOpenerWeb.configure do |config|
  config.letters_location = Rails.root.join('your', 'new', 'path')

Usage on pre-production environments

Some people use this gem on staging / pre-production environments to avoid having real emails being sent out. To set that up you'll need to:

  1. Move the gem out of the development group in your Gemfile
  2. Set config.action_mailer.delivery_method on the appropriate config/environments/<env>.rb
  3. Enable the route for the environments on your routes.rb.

In other words, your Gemfile will have:

gem 'letter_opener_web'

And your routes.rb:

Your::Application.routes.draw do
  # If you have a dedicated config/environments/staging.rb
  mount LetterOpenerWeb::Engine, at: "/letter_opener" if Rails.env.staging?

  # If you use RAILS_ENV=production in staging environments, you'll need another
  # way to disable it in "real production"
  mount LetterOpenerWeb::Engine, at: "/letter_opener" unless ENV["PRODUCTION_FOR_REAL"]

You might also want to have a look at the sources for the demo available at

NOTICE: Using this gem on Heroku will only work if your app has just one Dyno and does not send emails from background jobs. For updates on this matter please subscribe to GH-35


Special thanks to @alexrothenberg for some ideas on this pull request and @pseudomuto for keeping the project alive for a few years.


  1. Fork it and run bin/setup
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request