diff --git a/Gemfile b/Gemfile
index c7afeadd..783b9c6f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -232,6 +232,7 @@ group :development do
   gem 'rubocop-rspec'
   # to open mails
   gem 'letter_opener'
+  gem 'letter_opener_web'
   # as deployment system
   gem 'mina'
   # as debugger on error pages
diff --git a/Gemfile.lock b/Gemfile.lock
index d59269ab..07c4232f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -265,6 +265,10 @@ GEM
       rails (>= 4.2.0)
     letter_opener (1.7.0)
       launchy (~> 2.2)
+    letter_opener_web (1.4.0)
+      actionmailer (>= 3.2)
+      letter_opener (~> 1.0)
+      railties (>= 3.2)
     listen (3.1.5)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -665,6 +669,7 @@ DEPENDENCIES
   json-schema
   leaflet-rails
   letter_opener
+  letter_opener_web
   mina
   mini_magick
   money-rails
diff --git a/config/routes.rb b/config/routes.rb
index f6c4566d..1201b24c 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,4 +1,5 @@
 Osem::Application.routes.draw do
+  mount LetterOpenerWeb::Engine, at: '/letter_opener' if Rails.env.development?
 
   constraints DomainConstraint do
     get '/', to: 'conferences#show'