This guide provides you with all you need to get started in sending emails from and to your application, and many internals of Action Mailer. It also covers how to test your mailers.
After reading this guide, you will know:
Action Mailer allows you to send emails from your application using mailer classes and views.
They inherit from ActionMailer::Base and live in app/mailers. Mailers also work very similarly to controllers. Some examples of similarities are enumerated below. Mailers have:
app/views.This section will provide a step-by-step guide to creating a mailer and its views.
$ rails generate mailer UserMailer create app/mailers/user_mailer.rb create app/mailers/application_mailer.rb invoke erb create app/views/user_mailer create app/views/layouts/mailer.text.erb create app/views/layouts/mailer.html.erb invoke test_unit create test/mailers/user_mailer_test.rb create test/mailers/previews/user_mailer_preview.rb
# app/mailers/application_mailer.rb class ApplicationMailer < ActionMailer::Base default from: "[email protected]" layout 'mailer' end # app/mailers/user_mailer.rb class UserMailer < ApplicationMailer end
As you can see, you can generate mailers just like you use other generators with Rails.
If you didn't want to use a generator, you could create your own file inside of app/mailers, just make sure that it inherits from ActionMailer::Base:
class MyMailer < ActionMailer::Base end
Mailers have methods called "actions" and they use views to structure their content. Where a controller generates content like HTML to send back to the client, a Mailer creates a message to be delivered via email.
app/mailers/user_mailer.rb contains an empty mailer:
class UserMailer < ApplicationMailer end
Let's add a method called welcome_email, that will send an email to the user's registered email address:
class UserMailer < ApplicationMailer default from: '[email protected]' def welcome_email @user = params[:user] @url = 'http://example.com/login' mail(to: @user.email, subject: 'Welcome to My Awesome Site') end end
Here is a quick explanation of the items presented in the preceding method. For a full list of all available options, please have a look further down at the Complete List of Action Mailer user-settable attributes section.
default Hash - This is a hash of default values for any email you send from this mailer. In this case we are setting the :from header to a value for all messages in this class. This can be overridden on a per-email basis.mail - The actual email message, we are passing the :to and :subject headers in.Create a file called welcome_email.html.erb in app/views/user_mailer/. This will be the template used for the email, formatted in HTML:
<!DOCTYPE html>
<html>
<head>
<meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
</head>
<body>
<h1>Welcome to example.com, <%= @user.name %></h1>
<p>
You have successfully signed up to example.com,
your username is: <%= @user.login %>.<br>
</p>
<p>
To login to the site, just follow this link: <%= @url %>.
</p>
<p>Thanks for joining and have a great day!</p>
</body>
</html> Let's also make a text part for this email. Not all clients prefer HTML emails, and so sending both is best practice. To do this, create a file called welcome_email.text.erb in app/views/user_mailer/:
Welcome to example.com, <%= @user.name %> =============================================== You have successfully signed up to example.com, your username is: <%= @user.login %>. To login to the site, just follow this link: <%= @url %>. Thanks for joining and have a great day!
When you call the mail method now, Action Mailer will detect the two templates (text and HTML) and automatically generate a multipart/alternative email.
Mailers are really just another way to render a view. Instead of rendering a view and sending it over the HTTP protocol, they are just sending it out through the email protocols instead. Due to this, it makes sense to just have your controller tell the Mailer to send an email when a user is successfully created.
Setting this up is simple.
First, let's create a simple User scaffold:
$ rails generate scaffold user name email login $ rails db:migrate
Now that we have a user model to play with, we will just edit the app/controllers/users_controller.rb make it instruct the UserMailer to deliver an email to the newly created user by editing the create action and inserting a call to UserMailer.with(user: @user).welcome_email right after the user is successfully saved.
Action Mailer is nicely integrated with Active Job so you can send emails outside of the request-response cycle, so the user doesn't have to wait on it:
class UsersController < ApplicationController
# POST /users
# POST /users.json
def create
@user = User.new(params[:user])
respond_to do |format|
if @user.save
# Tell the UserMailer to send a welcome email after save
UserMailer.with(user: @user).welcome_email.deliver_later
format.html { redirect_to(@user, notice: 'User was successfully created.') }
format.json { render json: @user, status: :created, location: @user }
else
format.html { render action: 'new' }
format.json { render json: @user.errors, status: :unprocessable_entity }
end
end
end
end Active Job's default behavior is to execute jobs via the :async adapter. So, you can use deliver_later now to send emails asynchronously. Active Job's default adapter runs jobs with an in-process thread pool. It's well-suited for the development/test environments, since it doesn't require any external infrastructure, but it's a poor fit for production since it drops pending jobs on restart. If you need a persistent backend, you will need to use an Active Job adapter that has a persistent backend (Sidekiq, Resque, etc).
When calling deliver_later the job will be placed under mailers queue. Make sure Active Job adapter support it otherwise the job may be silently ignored preventing email delivery. You can change that by specifying config.action_mailer.deliver_later_queue_name option.
If you want to send emails right away (from a cronjob for example) just call deliver_now:
class SendWeeklySummary
def run
User.find_each do |user|
UserMailer.with(user: user).weekly_summary.deliver_now
end
end
end Any key value pair passed to with just becomes the params for the mailer action. So with(user: @user, account: @user.account) makes params[:user] and params[:account] available in the mailer action. Just like controllers have params.
The method welcome_email returns an ActionMailer::MessageDelivery object which can then just be told deliver_now or deliver_later to send itself out. The ActionMailer::MessageDelivery object is just a wrapper around a Mail::Message. If you want to inspect, alter, or do anything else with the Mail::Message object you can access it with the message method on the ActionMailer::MessageDelivery object.
Action Mailer handles the auto encoding of multibyte characters inside of headers and bodies.
For more complex examples such as defining alternate character sets or self-encoding text first, please refer to the Mail library.
There are just three methods that you need to send pretty much any email message:
headers - Specifies any header on the email you want. You can pass a hash of header field names and value pairs, or you can call headers[:field_name] =
'value'.attachments - Allows you to add attachments to your email. For example, attachments['file-name.jpg'] = File.read('file-name.jpg').mail - Sends the actual email itself. You can pass in headers as a hash to the mail method as a parameter, mail will then create an email, either plain text, or multipart, depending on what email templates you have defined.Action Mailer makes it very easy to add attachments.
Pass the file name and content and Action Mailer and the Mail gem will automatically guess the mime_type, set the encoding, and create the attachment.
attachments['filename.jpg'] = File.read('/path/to/filename.jpg') When the mail method will be triggered, it will send a multipart email with an attachment, properly nested with the top level being multipart/mixed and the first part being a multipart/alternative containing the plain text and HTML email messages.
Mail will automatically Base64 encode an attachment. If you want something different, encode your content and pass in the encoded content and encoding in a Hash to the attachments method.
Pass the file name and specify headers and content and Action Mailer and Mail will use the settings you pass in.
encoded_content = SpecialEncode(File.read('/path/to/filename.jpg'))
attachments['filename.jpg'] = {
mime_type: 'application/gzip',
encoding: 'SpecialEncoding',
content: encoded_content
} If you specify an encoding, Mail will assume that your content is already encoded and not try to Base64 encode it.
Action Mailer 3.0 makes inline attachments, which involved a lot of hacking in pre 3.0 versions, much simpler and trivial as they should be.
First, to tell Mail to turn an attachment into an inline attachment, you just call #inline on the attachments method within your Mailer:
def welcome
attachments.inline['image.jpg'] = File.read('/path/to/image.jpg')
end Then in your view, you can just reference attachments as a hash and specify which attachment you want to show, calling url on it and then passing the result into the image_tag method:
<p>Hello there, this is our image</p> <%= image_tag attachments['image.jpg'].url %>
As this is a standard call to image_tag you can pass in an options hash after the attachment URL as you could for any other image:
<p>Hello there, this is our image</p> <%= image_tag attachments['image.jpg'].url, alt: 'My Photo', class: 'photos' %>
It is possible to send email to one or more recipients in one email (e.g., informing all admins of a new signup) by setting the list of emails to the :to key. The list of emails can be an array of email addresses or a single string with the addresses separated by commas.
class AdminMailer < ApplicationMailer
default to: -> { Admin.pluck(:email) },
from: '[email protected]'
def new_registration(user)
@user = user
mail(subject: "New User Signup: #{@user.email}")
end
end The same format can be used to set carbon copy (Cc:) and blind carbon copy (Bcc:) recipients, by using the :cc and :bcc keys respectively.
Sometimes you wish to show the name of the person instead of just their email address when they receive the email. The trick to doing that is to format the email address in the format "Full Name" <email>.
def welcome_email
@user = params[:user]
email_with_name = %("#{@user.name}" <#{@user.email}>)
mail(to: email_with_name, subject: 'Welcome to My Awesome Site')
end Mailer views are located in the app/views/name_of_mailer_class directory. The specific mailer view is known to the class because its name is the same as the mailer method. In our example from above, our mailer view for the welcome_email method will be in app/views/user_mailer/welcome_email.html.erb for the HTML version and welcome_email.text.erb for the plain text version.
To change the default mailer view for your action you do something like:
class UserMailer < ApplicationMailer default from: '[email protected]' def welcome_email @user = params[:user] @url = 'http://example.com/login' mail(to: @user.email, subject: 'Welcome to My Awesome Site', template_path: 'notifications', template_name: 'another') end end
In this case it will look for templates at app/views/notifications with name another. You can also specify an array of paths for template_path, and they will be searched in order.
If you want more flexibility you can also pass a block and render specific templates or even render inline or text without using a template file:
class UserMailer < ApplicationMailer default from: '[email protected]' def welcome_email @user = params[:user] @url = 'http://example.com/login' mail(to: @user.email, subject: 'Welcome to My Awesome Site') do |format| format.html { render 'another_template' } format.text { render plain: 'Render text' } end end end
This will render the template 'another_template.html.erb' for the HTML part and use the rendered text for the text part. The render command is the same one used inside of Action Controller, so you can use all the same options, such as :text, :inline etc.
If you would like to render a template located outside of the default app/views/mailer_name/ directory, you can apply the prepend_view_path, like so:
class UserMailer < ApplicationMailer
prepend_view_path "custom/path/to/mailer/view"
# This will try to load "custom/path/to/mailer/view/welcome_email" template
def welcome_email
# ...
end
end You can also consider using the append_view_path method.
You can perform fragment caching in mailer views like in application views using the cache method.
<% cache do %> <%= @company.name %> <% end %>
And in order to use this feature, you need to configure your application with this:
config.action_mailer.perform_caching = true
Fragment caching is also supported in multipart emails. Read more about caching in the Rails caching guide.
Just like controller views, you can also have mailer layouts. The layout name needs to be the same as your mailer, such as user_mailer.html.erb and user_mailer.text.erb to be automatically recognized by your mailer as a layout.
In order to use a different file, call layout in your mailer:
class UserMailer < ApplicationMailer layout 'awesome' # use awesome.(html|text).erb as the layout end
Just like with controller views, use yield to render the view inside the layout.
You can also pass in a layout: 'layout_name' option to the render call inside the format block to specify different layouts for different formats:
class UserMailer < ApplicationMailer
def welcome_email
mail(to: params[:user].email) do |format|
format.html { render layout: 'my_layout' }
format.text
end
end
end Will render the HTML part using the my_layout.html.erb file and the text part with the usual user_mailer.text.erb file if it exists.
Action Mailer previews provide a way to see how emails look by visiting a special URL that renders them. In the above example, the preview class for UserMailer should be named UserMailerPreview and located in test/mailers/previews/user_mailer_preview.rb. To see the preview of welcome_email, implement a method that has the same name and call UserMailer.welcome_email:
class UserMailerPreview < ActionMailer::Preview
def welcome_email
UserMailer.with(user: User.first).welcome_email
end
end Then the preview will be available in http://localhost:3000/rails/mailers/user_mailer/welcome_email.
If you change something in app/views/user_mailer/welcome_email.html.erb or the mailer itself, it'll automatically reload and render it so you can visually see the new style instantly. A list of previews are also available in http://localhost:3000/rails/mailers.
By default, these preview classes live in test/mailers/previews. This can be configured using the preview_path option. For example, if you want to change it to lib/mailer_previews, you can configure it in config/application.rb:
config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews" Unlike controllers, the mailer instance doesn't have any context about the incoming request so you'll need to provide the :host parameter yourself.
As the :host usually is consistent across the application you can configure it globally in config/application.rb:
config.action_mailer.default_url_options = { host: 'example.com' } Because of this behavior you cannot use any of the *_path helpers inside of an email. Instead you will need to use the associated *_url helper. For example instead of using
<%= link_to 'welcome', welcome_path %>
You will need to use:
<%= link_to 'welcome', welcome_url %>
By using the full URL, your links will now work in your emails.
url_forurl_for generates a full URL by default in templates.
If you did not configure the :host option globally make sure to pass it to url_for.
<%= url_for(host: 'example.com',
controller: 'welcome',
action: 'greeting') %> Email clients have no web context and so paths have no base URL to form complete web addresses. Thus, you should always use the "_url" variant of named route helpers.
If you did not configure the :host option globally make sure to pass it to the URL helper.
<%= user_url(@user, host: 'example.com') %>
non-GET links require rails-ujs or jQuery UJS, and won't work in mailer templates. They will result in normal GET requests.
Unlike controllers, the mailer instance doesn't have any context about the incoming request so you'll need to provide the :asset_host parameter yourself.
As the :asset_host usually is consistent across the application you can configure it globally in config/application.rb:
config.action_mailer.asset_host = 'http://example.com'
Now you can display an image inside your email.
<%= image_tag 'image.jpg' %>
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.erb and welcome_email.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.
The order of the parts getting inserted is determined by the :parts_order inside of the ActionMailer::Base.default method.
If you wish to override the default delivery options (e.g. SMTP credentials) while delivering emails, you can do this using delivery_method_options in the mailer action.
class UserMailer < ApplicationMailer
def welcome_email
@user = params[:user]
@url = user_url(@user)
delivery_options = { user_name: params[:company].smtp_user,
password: params[:company].smtp_password,
address: params[:company].smtp_host }
mail(to: @user.email,
subject: "Please see the Terms and Conditions attached",
delivery_method_options: delivery_options)
end
end There may be cases in which you want to skip the template rendering step and supply the email body as a string. You can achieve this using the :body option. In such cases don't forget to add the :content_type option. Rails will default to text/plain otherwise.
class UserMailer < ApplicationMailer
def welcome_email
mail(to: params[:user].email,
body: params[:email_body],
content_type: "text/html",
subject: "Already rendered!")
end
end Action Mailer allows for you to specify a before_action, after_action and around_action.
Filters can be specified with a block or a symbol to a method in the mailer class similar to controllers.
You could use a before_action to populate the mail object with defaults, delivery_method_options or insert default headers and attachments.
class InvitationsMailer < ApplicationMailer
before_action { @inviter, @invitee = params[:inviter], params[:invitee] }
before_action { @account = params[:inviter].account }
default to: -> { @invitee.email_address },
from: -> { common_address(@inviter) },
reply_to: -> { @inviter.email_address_with_name }
def account_invitation
mail subject: "#{@inviter.name} invited you to their Basecamp (#{@account.name})"
end
def project_invitation
@project = params[:project]
@summarizer = ProjectInvitationSummarizer.new(@project.bucket)
mail subject: "#{@inviter.name.familiar} added you to a project in Basecamp (#{@account.name})"
end
end after_action to do similar setup as a before_action but using instance variables set in your mailer action.class UserMailer < ApplicationMailer
before_action { @business, @user = params[:business], params[:user] }
after_action :set_delivery_options,
:prevent_delivery_to_guests,
:set_business_headers
def feedback_message
end
def campaign_message
end
private
def set_delivery_options
# You have access to the mail instance,
# @business and @user instance variables here
if @business && @business.has_smtp_settings?
mail.delivery_method.settings.merge!(@business.smtp_settings)
end
end
def prevent_delivery_to_guests
if @user && @user.guest?
mail.perform_deliveries = false
end
end
def set_business_headers
if @business
headers["X-SMTPAPI-CATEGORY"] = @business.code
end
end
end Action Mailer now just inherits from AbstractController, so you have access to the same generic helpers as you do in Action Controller.
The following configuration options are best made in one of the environment files (environment.rb, production.rb, etc...)
| Configuration | Description |
|---|---|
logger | Generates 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:
|
sendmail_settings | Allows you to override options for the :sendmail delivery method.
|
raise_delivery_errors | Whether or not errors should be raised if the email fails to be delivered. This only works if the external email server is configured for immediate delivery. |
delivery_method | Defines a delivery method. Possible values are:
|
perform_deliveries | Determines whether deliveries are actually carried out when the deliver method is invoked on the Mail message. By default they are, but this can be turned off to help functional testing. If this value is false, deliveries array will not be populated even if delivery_method is :test. |
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_options | Allows you to set default values for the mail method options (:from, :reply_to, etc.). |
For a complete writeup of possible configurations see the Configuring Action Mailer in our Configuring Rails Applications guide.
An example would be adding the following to your appropriate config/environments/$RAILS_ENV.rb file:
config.action_mailer.delivery_method = :sendmail
# Defaults to:
# config.action_mailer.sendmail_settings = {
# location: '/usr/sbin/sendmail',
# arguments: '-i'
# }
config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true
config.action_mailer.default_options = {from: '[email protected]'} As Action Mailer now uses the Mail gem, this becomes as simple as adding to your config/environments/$RAILS_ENV.rb file:
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 } As of July 15, 2014, Google increased its security measures and now blocks attempts from apps it deems less secure. You can change your Gmail settings here to allow the attempts. If your Gmail account has 2-factor authentication enabled, then you will need to set an app password and use that instead of your regular password. Alternatively, you can use another ESP to send email by replacing 'smtp.gmail.com' above with the address of your provider.
You can find detailed instructions on how to test your mailers in the testing guide.
Action Mailer provides hooks into the Mail observer and interceptor methods. These allow you to register classes that are called during the mail delivery life cycle of every email sent.
Interceptors allow you to make modifications to emails before they are handed off to the delivery agents. An interceptor class must implement the :delivering_email(message) method which will be called before the email is sent.
class SandboxEmailInterceptor
def self.delivering_email(message)
message.to = ['[email protected]']
end
end Before the interceptor can do its job you need to register it with the Action Mailer framework. You can do this in an initializer file config/initializers/sandbox_email_interceptor.rb
if Rails.env.staging? ActionMailer::Base.register_interceptor(SandboxEmailInterceptor) end
The example above uses a custom environment called "staging" for a production like server but for testing purposes. You can read Creating Rails environments for more information about custom Rails environments.
Observers give you access to the email message after it has been sent. An observer class must implement the :delivered_email(message) method, which will be called after the email is sent.
class EmailDeliveryObserver
def self.delivered_email(message)
EmailDelivery.log(message)
end
end Like interceptors, you need to register observers with the Action Mailer framework. You can do this in an initializer file config/initializers/email_delivery_observer.rb
ActionMailer::Base.register_observer(EmailDeliveryObserver)
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