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Action Mailer

Even if we mainly use Ruby on Rails to generate web pages, it sometimes is useful to be able to send an e-mail.

So let’s go and build an example with minimal user management for a web shop that automatically sends an e-mail to the user when a new user is created:

$ rails new webshop
  [...]
$ cd webshop
$ rails generate scaffold User name email
  [...]
$ rails db:migrate
  [...]

For the user model we create a minimal validation in the app/models/user.rb, so that we can be sure that each user has a name and a syntactically correct e-mail address.

app/models/user.rb
class User < ApplicationRecord
  validates :name,
            presence: true

  validates :email,
            presence: true,
            format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i }
end

There is a generator with the name mailer that creates the files required for mailing. First, we have a look at the output of the rails generate mailer, without passing any further arguments:

$ rails generate mailer
Running via Spring preloader in process 99958
Usage:
  rails generate mailer NAME [method method] [options]

[...]

Example:
========
    rails generate mailer Notifications signup forgot_password invoice

    creates a Notifications mailer class, views, and test:
        Mailer:     app/mailers/notifications_mailer.rb
        Views:      app/views/notifications_mailer/signup.text.erb [...]
        Test:       test/mailers/notifications_mailer_test.rb

That is just what we expected. So let’s now create the mailer notification:

$ rails generate mailer Notification new_account
Running via Spring preloader in process 201
      create  app/mailers/notification_mailer.rb
      invoke  erb
      create    app/views/notification_mailer
      create    app/views/notification_mailer/new_account.text.erb
      create    app/views/notification_mailer/new_account.html.erb
      invoke  test_unit
      create    test/mailers/notification_mailer_test.rb
      create    test/mailers/previews/notification_mailer_preview.rb

In the file app/mailers/notification_mailer.rb you will find the controller for it:

app/mailers/notification_mailer.rb
class NotificationMailer < ApplicationMailer

  # Subject can be set in your I18n file at config/locales/en.yml
  # with the following lookup:
  #
  #   en.notification_mailer.new_account.subject
  #
  def new_account
    @greeting = "Hi"

    mail to: "[email protected]"
  end
end

In it, we change the new_account method to accept a parameter with new_account(user)` and some code to use that to send the confirmation e-mail.

app/mailers/notification_mailer.rb
class NotificationMailer < ApplicationMailer
  def new_account(user)
    @user = user
    mail(to: user.email, subject: "Account #{user.name} is active")
  end
end

Now we create the view for this method. Actually we have to breath live into two files:

  • app/views/notification_mailer/new_account.text.erb

  • app/views/notification_mailer/new_account.html.erb

In case you want to send an non-HTML only e-mail you can delete the file app/views/notification_mailer/new_account.html.erb. Otherwise ActionMailer will generate an e-mail which can be read as a modern HTML or a traditional text one.

app/views/notification_mailer/new_account.text.erb
Hello <%= @user.name %>,

your new account is active.

Have a great day!
  A Robot
app/views/notification_mailer/new_account.html.erb
<p>Hello <%= @user.name %>,</p>
<p>your new account is active.</p>
<p>Have a great day!</br>
  A Robot</p>

As we want to send this e-mail after the create of a User, we still need add an after_create callback which triggers the delivery:

app/models/user.rb
class User < ApplicationRecord
  validates :name,
            presence: true

  validates :email,
            presence: true,
            format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i }

  after_create :send_welcome_email

  private
  def send_welcome_email
    NotificationMailer.new_account(self).deliver_later
  end
end

Let’s create a new User in the console.

Note
 I’ll take a moment for ActiveJob to send the email. Be patient. 
$ rails console
Running via Spring preloader in process 1795
Loading development environment (Rails 5.1.0)
>> User.create(name: "Wintermeyer", email: "[email protected]")
   (0.1ms)  begin transaction
  SQL (0.5ms)  INSERT INTO "users" ("name", "email", "created_at",
  "updated_at") VALUES (?, ?, ?, ?)  [["name", "Wintermeyer"],
  ["email", "[email protected]"], ["created_at",
  "2017-03-25 10:50:18.242475"], ["updated_at",
  "2017-03-25 10:50:18.242475"]]
Enqueued ActionMailer::DeliveryJob
(Job ID: a902ec6f-3b61-4c4c-8d75-d82acb663572) to Async(mailers) with
arguments: "NotificationMailer", "new_account", "deliver_now",
#<GlobalID:0x007fe31dcb3920 @uri=#<URI::GID gid://webshop/User/1>>
   (1.1ms)  commit transaction
=> #<User id: 1, name: "Wintermeyer", email: "[email protected]",
created_at: "2017-03-25 10:50:18", updated_at: "2017-03-25 10:50:18">
>>   User Load (0.1ms)  SELECT  "users".* FROM "users"
WHERE "users"."id" = ? LIMIT ?  [["id", 1], ["LIMIT", 1]]
Performing ActionMailer::DeliveryJob
(Job ID: a902ec6f-3b61-4c4c-8d75-d82acb663572) from Async(mailers) with
arguments: "NotificationMailer", "new_account", "deliver_now",
#<GlobalID:0x007fe31f800ac0 @uri=#<URI::GID gid://webshop/User/1>>
  Rendering notification_mailer/new_account.html.erb within layouts/mailer
  Rendered notification_mailer/new_account.html.erb within layouts/mailer (0.8ms)
  Rendering notification_mailer/new_account.text.erb within layouts/mailer
  Rendered notification_mailer/new_account.text.erb within layouts/mailer (0.3ms)
NotificationMailer#new_account: processed outbound mail in 141.0ms
Sent mail to [email protected] (26.2ms)
Date: Sat, 25 Mar 2017 11:50:28 +0100
From: [email protected]
To: [email protected]
Message-ID: <[email protected]>
Subject: Account Wintermeyer is active
Mime-Version: 1.0
Content-Type: multipart/alternative;
 boundary="--==_mimepart_58d64b749dc0c_7033ff18ee59aec39018";
 charset=UTF-8
Content-Transfer-Encoding: 7bit


----==_mimepart_58d64b749dc0c_7033ff18ee59aec39018
Content-Type: text/plain;
 charset=UTF-8
Content-Transfer-Encoding: 7bit

Hello Wintermeyer,

your new account is active.

Have a great day!
  A Robot


----==_mimepart_58d64b749dc0c_7033ff18ee59aec39018
Content-Type: text/html;
 charset=UTF-8
Content-Transfer-Encoding: 7bit

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <style>
      /* Email styles need to be inline */
    </style>
  </head>

  <body>
    <p>Hello Wintermeyer,</p>
<p>your new account is active.</p>
<p>Have a great day!</br>
  A Robot</p>

  </body>
</html>

----==_mimepart_58d64b749dc0c_7033ff18ee59aec39018--

Performed ActionMailer::DeliveryJob
(Job ID: a902ec6f-3b61-4c4c-8d75-d82acb663572) from Async(mailers)
in 177.32ms
>> exit

That was straightforward. In the development mode we see the e-mail in the log. In production mode it would be send to the configured SMTP gateway.

Note
 Have a look at the files app/views/layouts/mailer.html.erb and app/views/layouts/mailer.text.erb to set a generic envelope (e.g. add CSS) for your e-mail content. It works like app/views/layouts/application.html.erb for HTML views.

Configuring the E-Mail Server

Rails can use a local sendmail or an external SMTP server for delivering the e-mails.

Sending via Local Sendmail

If you want to send the e-mails in the traditional way via local sendmail, then you need to insert the following lines into your configuration file config/environments/development.rb (for the development environment) or config/environments/production.rb (for your production environment):

config/environments/development.rb
config.action_mailer.delivery_method = :sendmail
config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true

Sending via Direct SMTP

If you want to send the e-mail directly via a SMTP server (for example Google Mail), then you need to insert the following lines into your configuration file config/environments/development.rb (for the development environment) or config/environments/production.rb (for your production environment):

config/environments/development.rb
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address:              "smtp.gmail.com",
  port:                 587,
  domain:               'example.com',
  user_name:            '<username>',
  password:             '<password>',
  authentication:       'plain',
  enable_starttls_auto: true  }

Of course you need to adapt the values for :domain, :user_name and :password in accordance with your configuration.

Custom X-Header

If you feel the urge to integrate an additional X-header then this is no problem. Here is an example for expanding the file app/mailers/notification_mailer.rb:

app/mailers/notification_mailer.rb
class NotificationMailer < ApplicationMailer
  def new_account(user)
    @user = user
    headers["X-Priority"] = '3'
    mail(to: user.email, subject: "The account #{user.name} is active.")
  end
end

This means the sent e-mail would look like this:

Sent mail to [email protected] (50ms)
Date: Wed, 30 May 2012 17:35:21 +0200
From: [email protected]
To: [email protected]
Message-ID: <[email protected]>
Subject: The new account Wintermeyer is active.
Mime-Version: 1.0
Content-Type: text/plain;
 charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Priority: 3

Hello Wintermeyer,

your new account is active.

Have a great day!
  A Robot

Attachments

E-mail attachments are also defined in the controller.

As an example we add in app/mailers/notification_mailer.rb the Rails image app/assets/images/rails.png to an e-mail as attachment:

app/mailers/notification_mailer.rb
class NotificationMailer < ApplicationMailer
  def new_account(user)
    @user = user
    attachments['rails.png'] =
      File.read("#{Rails.root}/app/assets/images/rails.png")
    mail(to: user.email, subject: "The account #{user.name} is active.")
  end
end

Inline Attachments

For inline attachments in HTML e-mails, you need to use the method inline when calling attachments. In our example controller app/mailers/notification_mailer.rb:

app/mailers/notification_mailer.rb
class NotificationMailer < ApplicationMailer
  def new_account(user)
    @user = user
    attachments.inline['rails.png'] =
      File.read("#{Rails.root}/app/assets/images/rails.png")
    mail(to: user.email, subject: "The account #{user.name} is active.")
  end
end

In the HTML e-mail, you can access the hash attachments[] via image_tag. In our example the app/views/notification_mailer/new_account.html.erb would look like this:

app/views/notification_mailer/new_account.html.erb
<!DOCTYPE html>
<html>
  <head>
    <meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />
  </head>
  <body>
    <%= image_tag attachments['rails.png'].url, :alt => 'Rails Logo' %>
    <p>Hello <%= @user.name %>,</p>

    <p>your new account is active.</p>

    <p><i>Have a great day!</i></p>
    <p>A Robot</p>
  </body>
</html>

Further Information

The Rails online documentation has a very extensive entry on ActionMailer at http://guides.rubyonrails.org/action_mailer_basics.html.