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Action Mailer Basics

This guide should provide you with all you need to get started in sending and receiving emails from/to your application, and many internals of Action Mailer. It also covers how to test your mailers.

1 Introduction

Action Mailer allows you to send emails from your application using a mailer model and views. So, in Rails, emails are used by creating models that inherit from ActionMailer::Base that live alongside other models in app/models. Those models have associated views that appear alongside controller views in app/views.

2 Sending Emails

This section will provide a step-by-step guide to creating a mailer and its views.

2.1 Walkthrough to Generating a Mailer

2.1.1 Create the Mailer
./script/generate mailer UserMailer exists app/models/ create app/views/user_mailer exists test/unit/ create test/fixtures/user_mailer create app/models/user_mailer.rb create test/unit/user_mailer_test.rb

So we got the model, the fixtures, and the tests.

2.1.2 Edit the Model
app/models/user_mailer.rbcontains an empty mailer:
class UserMailer < ActionMailer::Base end

Let’s add a method called welcome_email, that will send an email to the user’s registered email address:

class UserMailer < ActionMailer::Base def welcome_email(user) recipients user.email from "My Awesome Site Notifications <notifications@example.com>" subject "Welcome to My Awesome Site" sent_on Time.now body {:user => user, :url => "http://example.com/login"} end end

Here is a quick explanation of the options presented in the preceding method. For a full list of all available options, please have a look further down at the Complete List of ActionMailer user-settable attributes section.

recipients The recipients of the email. It can be a string or, if there are multiple recipients, an array of strings
from The from address of the email
subject The subject of the email
sent_on The timestamp for the email

The keys of the hash passed to body become instance variables in the view. Thus, in our example the mailer view will have a @user and a @url instance variables available.

2.1.3 Create a Mailer View

Create a file called welcome_email.text.html.erb in app/views/user_mailer/. This will be the template used for the email, formatted in HTML:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <meta content="text/html; charset=UTF-8" http-equiv="Content-Type" /> </head> <body> <h1>Welcome to example.com, <%=h @user.first_name %></h1> <p> You have successfully signed up to example.com, and your username is: <%= @user.login %>.<br/> To login to the site, just follow this link: <%=h @url %>. </p> <p>Thanks for joining and have a great day!</p> </body> </html>

Had we wanted to send text-only emails, the file would have been called welcome_email.text.plain.erb. Rails sets the content type of the email to be the one in the filename.

2.1.4 Wire It Up So That the System Sends the Email When a User Signs Up

There are three ways to achieve this. One is to send the email from the controller that sends the email, another is to put it in a before_create callback in the user model, and the last one is to use an observer on the user model. Whether you use the second or third methods is up to you, but staying away from the first is recommended. Not because it’s wrong, but because it keeps your controller clean, and keeps all logic related to the user model within the user model. This way, whichever way a user is created (from a web form, or from an API call, for example), we are guaranteed that the email will be sent.

Let’s see how we would go about wiring it up using an observer:

In config/environment.rb:

Rails::Initializer.run do |config| # ... config.active_record.observers = :user_observer end

You can place the observer in app/models where it will be loaded automatically by Rails.

Now create a file called user_observer.rb in app/models depending on where you stored it, and make it look like:

class UserObserver < ActiveRecord::Observer def after_create(user) UserMailer.deliver_welcome_email(user) end end

Notice how we call deliver_welcome_email? In Action Mailer we send emails by calling deliver_<method_name>. In UserMailer, we defined a method called welcome_email, and so we deliver the email by calling deliver_welcome_email. The next section will go through how Action Mailer achieves this.

2.2 Action Mailer and Dynamic deliver_<method_name> methods

So how does Action Mailer understand this deliver_welcome_email call? If you read the documentation (http://api.rubyonrails.org/files/vendor/rails/actionmailer/README.html), you will find this in the “Sending Emails” section:

You never instantiate your mailer class. Rather, your delivery instance methods are automatically wrapped in class methods that start with the word deliver_ followed by the name of the mailer method that you would like to deliver.

So, how exactly does this work?

Looking at the ActionMailer::Base source, you will find this:

def method_missing(method_symbol, *parameters)#:nodoc: case method_symbol.id2name when /^create_([_a-z]\w*)/ then new($1, *parameters).mail when /^deliver_([_a-z]\w*)/ then new($1, *parameters).deliver! when "new" then nil else super end end

Hence, if the method name starts with deliver_ followed by any combination of lowercase letters or underscore, method_missing calls new on your mailer class (UserMailer in our example above), sending the combination of lower case letters or underscore, along with the parameters. The resulting object is then sent the deliver! method, which well… delivers it.

2.3 Complete List of Action Mailer User-Settable Attributes

bcc The BCC addresses of the email
body The body of the email. This is either a hash (in which case it specifies the variables to pass to the template when it is rendered), or a string, in which case it specifies the actual body of the message
cc The CC addresses for the email
charset The charset to use for the email. This defaults to the default_charset specified for ActionMailer::Base.
content_type The content type for the email. This defaults to “text/plain” but the filename may specify it
from The from address of the email
reply_to The address (if different than the “from” address) to direct replies to this email
headers Additional headers to be added to the email
implicit_parts_order The order in which parts should be sorted, based on the content type. This defaults to the value of default_implicit_parts_order
mime_version Defaults to “1.0”, but may be explicitly given if needed
recipient The recipient addresses of the email, either as a string (for a single address) or an array of strings (for multiple addresses)
sent_on The timestamp on which the message was sent. If unset, the header will be set by the delivery agent
subject The subject of the email
template The template to use. This is the “base” template name, without the extension or directory, and may be used to have multiple mailer methods share the same template

2.4 Mailer Views

Mailer views are located in the app/views/name_of_mailer_class directory. The specific mailer view is known to the class because it’s name is the same as the mailer method. So for example, in our example from above, our mailer view for the welcome_email method will be in app/views/user_mailer/welcome_email.text.html.erb for the HTML version and welcome_email.text.plain.erb for the plain text version.

To change the default mailer view for your action you do something like:

class UserMailer < ActionMailer::Base def welcome_email(user) recipients user.email from "My Awesome Site Notifications<notifications@example.com>" subject "Welcome to My Awesome Site" sent_on Time.now body {:user => user, :url => "http://example.com/login"} content_type "text/html" # use some_other_template.text.(html|plain).erb instead template "some_other_template" end

2.5 Action Mailer Layouts

Just like controller views, you can also have mailer layouts. The layout name needs to end in “_mailer” to be automatically recognized by your mailer as a layout. So in our UserMailer example, we need to call our layout user_mailer.text.(html|plain).erb. In order to use a different file just use:

class UserMailer < ActionMailer::Base layout 'awesome' # use awesome.text.(html|plain).erb as the layout end

Just like with controller views, use yield to render the view inside the layout.

2.6 Generating URLs in Action Mailer Views

URLs can be generated in mailer views using url_for or named routes. Unlike controllers, the mailer instance doesn’t have any context about the incoming request so 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") %>

Email clients have no web context and so paths have no base URL to form complete web addresses. Thus, when using named routes only the “_url” variant makes sense.

It is also possible to set a default host that will be used in all mailers by setting the :host option in the ActionMailer::Base.default_url_options hash as follows:

ActionMailer::Base.default_url_options[:host] = "example.com"

This can also be set as a configuration option in config/environment.rb:

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

If you set a default :host for your mailers you need to pass :only_path => false to url_for. Otherwise it doesn’t get included.

2.7 Sending Multipart Emails

Action Mailer will automatically send multipart emails if you have different templates for the same action. So, for our UserMailer example, if you have welcome_email.text.plain.erb and welcome_email.text.html.erb in app/views/user_mailer, Action Mailer will automatically send a multipart email with the HTML and text versions setup as different parts.

To explicitly specify multipart messages, you can do something like:

class UserMailer < ActionMailer::Base def welcome_email(user) recipients user.email_address subject "New account information" from "system@example.com" content_type "multipart/alternative" part :content_type => "text/html", :body => "<p>html content, can also be the name of an action that you call<p>" part "text/plain" do |p| p.body = "text content, can also be the name of an action that you call" end end end

2.8 Sending Emails with Attachments

Attachments can be added by using the attachment method:

class UserMailer < ActionMailer::Base def welcome_email(user) recipients user.email_address subject "New account information" from "system@example.com" content_type "multipart/alternative" attachment :content_type => "image/jpeg", :body => File.read("an-image.jpg") attachment "application/pdf" do |a| a.body = generate_your_pdf_here() end end end

2.9 Sending Multipart Emails with Attachments

Once you use the attachment method, ActionMailer will no longer automagically use the correct template based on the filename. You must declare which template you are using for each content type via the part method.

In the following example, there would be two template files, welcome_email_html.erb and welcome_email_plain.erb in the app/views/user_mailer folder.

class UserMailer < ActionMailer::Base def welcome_email(user) recipients user.email_address subject "New account information" from "system@example.com" content_type "multipart/alternative" part "text/html" do |p| p.body = render_message("welcome_email_html", :message => "<h1>HTML content</h1>") end part "text/plain" do |p| p.body = render_message("welcome_email_plain", :message => "text content") end attachment :content_type => "image/jpeg", :body => File.read("an-image.jpg") attachment "application/pdf" do |a| a.body = generate_your_pdf_here() end end end

3 Receiving Emails

Receiving and parsing emails with Action Mailer can be a rather complex endeavour. Before your email reaches your Rails app, you would have had to configure your system to somehow forward emails to your app, which needs to be listening for that. So, to receive emails in your Rails app you’ll need:

1. Implement a receive method in your mailer.

2. Configure your email server to forward emails from the address(es) you would like your app to receive to /path/to/app/script/runner 'UserMailer.receive(STDIN.read)'.

Once a method called receive is defined in any mailer, Action Mailer will parse the raw incoming email into an email object, decode it, instantiate a new mailer, and pass the email object to the mailer receive instance method. Here’s an example:

class UserMailer < ActionMailer::Base def receive(email) page = Page.find_by_address(email.to.first) page.emails.create( :subject => email.subject, :body => email.body ) if email.has_attachments? for attachment in email.attachments page.attachments.create({ :file => attachment, :description => email.subject }) end end end end

4 Using Action Mailer Helpers

Action Mailer classes have 4 helper methods available to them:

add_template_helper(helper_module) Makes all the (instance) methods in the helper module available to templates rendered through this controller.
helper(*args, &block) Declare a helper: helper :foo requires ‘foo_helper’ and includes FooHelper in the template class. helper FooHelper includes FooHelper in the template class. helper { def foo() “#{bar} is the very best” end } evaluates the block in the template class, adding method foo. helper(:three, BlindHelper) { def mice() ‘mice’ end } does all three.
helper_method Declare a controller method as a helper. For example, helper_method :link_to def link_to(name, options) … end makes the link_to controller method available in the view.
helper_attr Declare a controller attribute as a helper. For example, helper_attr :name attr_accessor :name makes the name and name= controller methods available in the view. The is a convenience wrapper for helper_method.

5 Action Mailer Configuration

The following configuration options are best made in one of the environment files (environment.rb, production.rb, etc…)

template_root Determines the base from which template references will be made.
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, :login, :cram_md5.
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.
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, and :test.
perform_deliveries Determines whether deliver_* methods are actually carried out. By default they are, but this can be turned off to help 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 The default charset used for the body and to encode the subject. Defaults to UTF-8. You can also pick a different charset from inside a method with charset.
default_content_type The default content type used for the main part of the message. Defaults to “text/plain”. You can also pick a different content type from inside a method with content_type.
default_mime_version The default mime version used for the message. Defaults to 1.0. You can also pick a different value from inside a method with mime_version.
default_implicit_parts_order 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. Defaults to [“text/html”, “text/enriched”, “text/plain”]. Items that appear first in the array have higher priority in the mail client and appear last in the mime encoded message. You can also pick a different order from inside a method with implicit_parts_order.

5.1 Example Action Mailer Configuration

An example would be:

ActionMailer::Base.delivery_method = :sendmail ActionMailer::Base.sendmail_settings = { :location => '/usr/sbin/sendmail', :arguments => '-i -t' } ActionMailer::Base.perform_deliveries = true ActionMailer::Base.raise_delivery_errors = true ActionMailer::Base.default_charset = "iso-8859-1"

5.2 Action Mailer Configuration for GMail

Instructions copied from http://http://www.fromjavatoruby.com/2008/11/actionmailer-with-gmail-must-issue.html

First you must install the action_mailer_tls plugin from http://code.openrain.com/rails/action_mailer_tls/, then all you have to do is configure action mailer.

ActionMailer::Base.smtp_settings = { :address => "smtp.gmail.com", :port => 587, :domain => "domain.com", :user_name => "user@domain.com", :password => "password", :authentication => :plain }

5.3 Configure Action Mailer to Recognize HAML Templates

In config/environment.rb, add the following line:

ActionMailer::Base.register_template_extension('haml')

6 Mailer Testing

By default Action Mailer does not send emails in the test environment. They are just added to the ActionMailer::Base.deliveries array.

Testing mailers normally involves two things: One is that the mail was queued, and the other one that the email is correct. With that in mind, we could test our example mailer from above like so:

class UserMailerTest < ActionMailer::TestCase tests UserMailer def test_welcome_email user = users(:some_user_in_your_fixtures) # Send the email, then test that it got queued email = UserMailer.deliver_welcome_email(user) assert !ActionMailer::Base.deliveries.empty? # Test the body of the sent email contains what we expect it to assert_equal [@user.email], email.to assert_equal "Welcome to My Awesome Site", email.subject assert_match /Welcome to example.com, #{user.first_name}/, email.body end end

In the test we send the email and store the returned object in the email variable. We then ensure that it was sent (the first assert), then, in the second batch of assertions, we ensure that the email does indeed contain the what we expect.

7 Changelog

Lighthouse ticket