Action Mailer allows you to send email from your application using a mailer model and views.

Mailer Models

To use Action Mailer, you need to create a mailer model.

$ rails generate mailer Notifier

The generated model inherits from ActionMailer::Base. Emails are defined by creating methods within the model which are then used to set variables to be used in the mail template, to change options on the mail, or to add attachments.

Examples:

class Notifier < ActionMailer::Base
  default :from => 'no-reply@example.com',
          :return_path => 'system@example.com'

  def welcome(recipient)
    @account = recipient
    mail(:to => recipient.email_address_with_name,
         :bcc => ["bcc@example.com", "Order Watcher <watcher@example.com>"])
    end
  end

Within the mailer method, you have access to the following methods:

• attachments[]= - Allows you to add attachments to your email in an intuitive manner; attachments = File.read('path/to/filename.png')

• attachments.inline[]= - Allows you to add an inline attachment to your email in the same manner as attachments[]=

• headers[]= - Allows you to specify any header field in your email such as headers['X-No-Spam'] = 'True'. Note, while most fields like To: From: can only appear once in an email header, other fields like X-Anything can appear multiple times. If you want to change a field that can appear multiple times, you need to set it to nil first so that Mail knows you are replacing it and not adding another field of the same name.

• headers(hash) - Allows you to specify multiple headers in your email such as headers({'X-No-Spam' => 'True', 'In-Reply-To' => '1234@message.id'})

• mail - Allows you to specify email to be sent.

The hash passed to the mail method allows you to specify any header that a Mail::Message will accept (any valid Email header including optional fields).

The mail method, if not passed a block, will inspect your views and send all the views with the same name as the method, so the above action would send the welcome.text.plain.erb view file as well as the welcome.text.html.erb view file in a multipart/alternative email.

If you want to explicitly render only certain templates, pass a block:

mail(:to => user.email) do |format|
  format.text
  format.html
end

The block syntax is also useful in providing information specific to a part:

mail(:to => user.email) do |format|
  format.text(:content_transfer_encoding => "base64")
  format.html
end

Or even to render a special view:

mail(:to => user.email) do |format|
  format.text
  format.html { render "some_other_template" }
end

Mailer views

Like Action Controller, each mailer class has a corresponding view directory in which each method of the class looks for a template with its name.

To define a template to be used with a mailing, create an .erb file with the same name as the method in your mailer model. For example, in the mailer defined above, the template at app/views/notifier/signup_notification.text.plain.erb would be used to generate the email.

Variables defined in the model are accessible as instance variables in the view.

Emails by default are sent in plain text, so a sample view for our model example might look like this:

Hi <%= @account.name %>,
Thanks for joining our service! Please check back often.

You can even use Action Pack helpers in these views. For example:

You got a new note!
<%= truncate(@note.body, 25) %>

If you need to access the subject, from or the recipients in the view, you can do that through message object:

You got a new note from <%= message.from %>!
<%= truncate(@note.body, 25) %>

Generating URLs

URLs can be generated in mailer views using url_for or named routes. Unlike controllers from Action Pack, the mailer instance doesn’t have any context about the incoming request, so you’ll need to provide all of the details needed to generate a URL.

When using url_for you’ll need to provide the :host, :controller, and :action:

<%= url_for(:host => "example.com", :controller => "welcome", :action => "greeting") %>

When using named routes you only need to supply the :host:

<%= users_url(:host => "example.com") %>

You want to avoid using the name_of_route_path form of named routes because it doesn’t make sense to generate relative URLs in email messages.

It is also possible to set a default host that will be used in all mailers by setting the :host option as a configuration option in config/application.rb:

config.action_mailer.default_url_options = { :host => "example.com" }

Setting ActionMailer::Base.default_url_options directly is now deprecated, use the configuration option mentioned above to set the default host.

If you do decide to set a default :host for your mailers you want to use the :only_path => false option when using url_for. This will ensure that absolute URLs are generated because the url_for view helper will, by default, generate relative URLs when a :host option isn’t explicitly provided.

Sending mail

Once a mailer action and template are defined, you can deliver your message or create it and save it for delivery later:

Notifier.welcome(david).deliver # sends the email
mail = Notifier.welcome(david)  # => a Mail::Message object
mail.deliver                    # sends the email

You never instantiate your mailer class. Rather, you just call the method you defined on the class itself.

Multipart Emails

Multipart messages can also be used implicitly because Action Mailer will automatically detect and use multipart templates, where each template is named after the name of the action, followed by the content type. Each such detected template will be added as separate part to the message.

For example, if the following templates exist:

• signup_notification.text.plain.erb

• signup_notification.text.html.erb

• signup_notification.text.xml.builder

• signup_notification.text.yaml.erb

Each would be rendered and added as a separate part to the message, with the corresponding content type. The content type for the entire message is automatically set to multipart/alternative, which indicates that the email contains multiple different representations of the same email body. The same instance variables defined in the action are passed to all email templates.

Implicit template rendering is not performed if any attachments or parts have been added to the email. This means that you’ll have to manually add each part to the email and set the content type of the email to multipart/alternative.

Attachments

Sending attachment in emails is easy:

class ApplicationMailer < ActionMailer::Base
  def welcome(recipient)
    attachments['free_book.pdf'] = File.read('path/to/file.pdf')
    mail(:to => recipient, :subject => "New account information")
  end
end

Which will (if it had both a welcome.text.plain.erb and welcome.text.html.erb template in the view directory), send a complete multipart/mixed email with two parts, the first part being a multipart/alternative with the text and HTML email parts inside, and the second being a application/pdf with a Base64 encoded copy of the file.pdf book with the filename free_book.pdf.

Inline Attachments

You can also specify that a file should be displayed inline with other HTML. This is useful if you want to display a corporate logo or a photo.

class ApplicationMailer < ActionMailer::Base
  def welcome(recipient)
    attachments.inline['photo.png'] = File.read('path/to/photo.png')
    mail(:to => recipient, :subject => "Here is what we look like")
  end
end

And then to reference the image in the view, you create a welcome.html.erb file and make a call to image_tag passing in the attachment you want to display and then call url on the attachment to get the relative content id path for the image source:

<h1>Please Don't Cringe</h1>

<%= image_tag attachments['photo.png'].url -%>

As we are using Action View’s image_tag method, you can pass in any other options you want:

<h1>Please Don't Cringe</h1>

<%= image_tag attachments['photo.png'].url, :alt => 'Our Photo', :class => 'photo' -%>

Observing and Intercepting Mails

Action Mailer provides hooks into the Mail observer and interceptor methods. These allow you to register objects that are called during the mail delivery life cycle.

An observer object must implement the :delivered_email(message) method which will be called once for every email sent after the email has been sent.

An interceptor object must implement the :delivering_email(message) method which will be called before the email is sent, allowing you to make modifications to the email before it hits the delivery agents. Your object should make and needed modifications directly to the passed in Mail::Message instance.

Default Hash

Action Mailer provides some intelligent defaults for your emails, these are usually specified in a default method inside the class definition:

class Notifier < ActionMailer::Base
  default :sender => 'system@example.com'
end

You can pass in any header value that a Mail::Message accepts. Out of the box, ActionMailer::Base sets the following:

• :mime_version => "1.0"

• :charset => "UTF-8",

• :content_type => "text/plain",

• :parts_order => [ "text/plain", "text/enriched", "text/html" ]

parts_order and charset are not actually valid Mail::Message header fields, but Action Mailer translates them appropriately and sets the correct values.

As you can pass in any header, you need to either quote the header as a string, or pass it in as an underscorised symbol, so the following will work:

class Notifier < ActionMailer::Base
  default 'Content-Transfer-Encoding' => '7bit',
          :content_description => 'This is a description'
end

Finally, Action Mailer also supports passing Proc objects into the default hash, so you can define methods that evaluate as the message is being generated:

class Notifier < ActionMailer::Base
  default 'X-Special-Header' => Proc.new { my_method }

  private

    def my_method
      'some complex call'
    end
end

Note that the proc is evaluated right at the start of the mail message generation, so if you set something in the defaults using a proc, and then set the same thing inside of your mailer method, it will get over written by the mailer method.

Configuration options

These options are specified on the class level, like ActionMailer::Base.raise_delivery_errors = true

• default - You can pass this in at a class level as well as within the class itself as per the above section.

• logger - the logger is used for generating information on the mailing run if available. Can be set to nil for no logging. Compatible with both Ruby’s own Logger and Log4r loggers.

• smtp_settings - Allows detailed configuration for :smtp delivery method:

  • :address - Allows you to use a remote mail server. Just change it from its default “localhost” setting.

  • :port - On the off chance that your mail server doesn’t run on port 25, you can change it.

  • :domain - If you need to specify a HELO domain, you can do it here.

  • :user_name - If your mail server requires authentication, set the username in this setting.

  • :password - If your mail server requires authentication, set the password in this setting.

  • :authentication - If your mail server requires authentication, you need to specify the authentication type here. This is a symbol and one of :plain (will send the password in the clear), :login (will send password BASE64 encoded) or :cram_md5 (combines a Challenge/Response mechanism to exchange information and a cryptographic Message Digest 5 algorithm to hash important information)

  • :enable_starttls_auto - When set to true, detects if STARTTLS is enabled in your SMTP server and starts to use it.

• sendmail_settings - Allows you to override options for the :sendmail delivery method.

  • :location - The location of the sendmail executable. Defaults to /usr/sbin/sendmail.

  • :arguments - The command line arguments. Defaults to -i -t with -f sender@addres added automatically before the message is sent.

• file_settings - Allows you to override options for the :file delivery method.

  • :location - The directory into which emails will be written. Defaults to the application tmp/mails.

• raise_delivery_errors - Whether or not errors should be raised if the email fails to be delivered.

• delivery_method - Defines a delivery method. Possible values are :smtp (default), :sendmail, :test, and :file. Or you may provide a custom delivery method object eg. MyOwnDeliveryMethodClass.new. See the Mail gem documentation on the interface you need to implement for a custom delivery agent.

• perform_deliveries - Determines whether emails are actually sent from Action Mailer when you call .deliver on an mail message or on an Action Mailer method. This is on by default but can be turned off to aid in functional testing.

• deliveries - Keeps an array of all the emails sent out through the Action Mailer with delivery_method :test. Most useful for unit and functional testing.

• default_charset - This is now deprecated, use the default method above to set the default :charset.

• default_content_type - This is now deprecated, use the default method above to set the default :content_type.

• default_mime_version - This is now deprecated, use the default method above to set the default :mime_version.

• default_implicit_parts_order - This is now deprecated, use the default method above to set the default :parts_order. Parts Order is used when a message is built implicitly (i.e. multiple parts are assembled from templates which specify the content type in their filenames) this variable controls how the parts are ordered.

actionmailer/lib/action_mailer/base.rb