Action Mailer – Easy email delivery and testing

Action Mailer is a framework for designing email service layers. These layers are used to consolidate code for sending out forgotten passwords, welcome wishes on signup, invoices for billing, and any other use case that requires a written notification to either a person or another system.

Action Mailer is in essence a wrapper around Action Controller and the Mail gem. It provides a way to make emails using templates in the same way that Action Controller renders views using templates.

Additionally, an Action Mailer class can be used to process incoming email, such as allowing a blog to accept new posts from an email (which could even have been sent from a phone).

You can read more about Action Mailer in the Action Mailer Basics guide.

Sending emails

The framework works by initializing any instance variables you want to be available in the email template, followed by a call to mail to deliver the email.

This can be as simple as:

class Notifier < ActionMailer::Base
  default from: 'system@loudthinking.com'

  def welcome(recipient)
    @recipient = recipient
    mail(to: recipient,
         subject: "[Signed up] Welcome #{recipient}")
  end
end

The body of the email is created by using an Action View template (regular ERB) that has the instance variables that are declared in the mailer action.

So the corresponding body template for the method above could look like this:

Hello there,

Mr. <%= @recipient %>

Thank you for signing up!

If the recipient was given as “david@loudthinking.com”, the email generated would look like this:

Date: Mon, 25 Jan 2010 22:48:09 +1100
From: system@loudthinking.com
To: david@loudthinking.com
Message-ID: <4b5d84f9dd6a5_7380800b81ac29578@void.loudthinking.com.mail>
Subject: [Signed up] Welcome david@loudthinking.com
Mime-Version: 1.0
Content-Type: text/plain;
      charset="US-ASCII";
Content-Transfer-Encoding: 7bit

Hello there,

Mr. david@loudthinking.com

Thank you for signing up!

In order to send mails, you simply call the method and then call deliver_now on the return value.

Calling the method returns a Mail Message object:

message = Notifier.welcome("david@loudthinking.com")   # => Returns a Mail::Message object
message.deliver_now                                    # => delivers the email

Or you can just chain the methods together like:

Notifier.welcome("david@loudthinking.com").deliver_now # Creates the email and sends it immediately

Setting defaults

It is possible to set default values that will be used in every method in your Action Mailer class. To implement this functionality, you just call the public class method default which you get for free from ActionMailer::Base. This method accepts a Hash as the parameter. You can use any of the headers, email messages have, like :from as the key. You can also pass in a string as the key, like “Content-Type”, but Action Mailer does this out of the box for you, so you won’t need to worry about that. Finally, it is also possible to pass in a Proc that will get evaluated when it is needed.

Note that every value you set with this method will get overwritten if you use the same key in your mailer method.

Example:

class AuthenticationMailer < ActionMailer::Base
  default from: "awesome@application.com", subject: Proc.new { "E-mail was generated at #{Time.now}" }
  .....
end

Configuration

The Base class has the full list of configuration options. Here’s an example:

ActionMailer::Base.smtp_settings = {
  address:        'smtp.yourserver.com', # default: localhost
  port:           '25',                  # default: 25
  user_name:      'user',
  password:       'pass',
  authentication: :plain                 # :plain, :login or :cram_md5
}