# How to preview emails with ActionMailer::Preview on Rails
We know how it's a pain to test ** e-mails** in our dev environment. Thinking of it, on Rails 4.1, the **ActionMailer::Preview** was released, making it possible to view e-mails without actually sending them. Let's learn how to use this tool.
First of all, we need to create a new mailer in our project.
```
rails generate mailer Welcome
Running via Spring preloader in process 5087
create app/mailers/welcome_mailer.rb
invoke erb
create app/views/welcome_mailer
invoke test_unit
create test/mailers/welcome_mailer_test.rb
create test/mailers/previews/welcome_mailer_preview.rb
```
It's possible to see that Rails created to files inside test filter: _test/mailers/welcome_mailer_test.rb_ and _test/mailers/previews/welcome_mailer_preview.rb_. In our case, we are going to use **_test/mailers/previews/welcome_mailer_preview.rb_** to preview our templates.
Now let's create a method inside **WelcomeMailer** that will be responsible for sending a welcome message to users that signup in our system, assuming we have a model User with an e-mail attribute. To do that, we need to open the file _app/mailers/welcome_mailer.rb_
```ruby
class WelcomeMailer < ApplicationMailer
def send_welcome_email(user)
@user = user
mail({
to: user.email,
from: 'eu@mauricioackermann.com.br',
subject: 'Seja bem-vindo ao sistema Maurício Ackermann'
})
end
end
```
Since **WelcomeMailer** is inheriting from ApplicationMailer, he will use the _mailer_ default layout
```ruby
class ApplicationMailer < ActionMailer::Base
default from: 'from@example.com'
layout 'mailer'
end
```
_app/layouts/mailer.html.erb_
```erb
<%= yield %>
```
At last, we need to create an e-mail template. Let's create a file __*send_welcome_email.html.erb*__ inside the folder _app/views/welcome_mailer_, which will be our e-mail view.
```erb
Hello, <%= @user.name %>
Thank you for registering in our system!
```
Now that we have our mailer and template done let's test it. All **e-mail previews** are in _test/mailers/previews_. Open the file created by our generator, **_welcome_mailer_preview.html.erb_**.
```ruby
class WelcomeMailerPreview < ActionMailer::Preview
def send_welcome_email
WelcomeMailer.send_welcome_email(User.new(name: 'Maurício Ackermann', email: 'eu@mauricioackermann.com.br'))
end
end
```
Now to visualize the e-mail, we start the server and access the **link**
http://localhost:3000/rails/mailers/welcome_mailer/send_welcome_email
Did you know about this Rails feature? I hope this post helps you debugging your **projects**