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
. A mailer model defines methods used to generate an
email message. In these methods, you can setup variables to be used in the
mailer views, options on the mail itself such as the :from
address, and attachments.
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['filename.png'] = File.read('path/to/filename.png')
-
attachments.inline[]=
- Allows you to add an inline attachment to your email in the same manner asattachments[]=
-
headers[]=
- Allows you to specify any header field in your email such asheaders['X-No-Spam'] = 'True'
. Note, while most fields likeTo:
From:
can only appear once in an email header, other fields likeX-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 asheaders({'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.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/welcome.text.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, length: 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, length: 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 should use the named_route_url
style (which generates
absolute URLs) and avoid using the named_route_path
style
(which generates relative URLs), since clients reading the mail will have
no concept of a current URL from which to determine a relative path.
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" }
When you decide to set a default :host
for your mailers, then
you need to make sure to use the only_path: false
option when
using url_for
. Since the url_for
view helper will
generate relative URLs by default when a :host
option
isn't explicitly provided, passing only_path: false
will
ensure that absolute URLs are generated.
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 a separate part to the message.
For example, if the following templates exist:
-
signup_notification.text.erb
-
signup_notification.html.erb
-
signup_notification.xml.builder
-
signup_notification.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.erb
and
welcome.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
.
If you need to send attachments with no content, you need to create an empty view for it, or add an empty body parameter like this:
class ApplicationMailer < ActionMailer::Base def welcome(recipient) attachments['free_book.pdf'] = File.read('path/to/file.pdf') mail(to: recipient, subject: "New account information", body: "") end end
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 classes that are called during the mail delivery life cycle.
An observer class must implement the :delivered_email(message)
method which will be called once for every email sent after the email has
been sent.
An interceptor class 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 class should make any 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 underscored 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.
It is also possible to set these default options that will be used in all
mailers through the default_options=
configuration in
config/application.rb
:
config.action_mailer.default_options = { from: "no-reply@example.org" }
Callbacks
You can specify callbacks using before_action and after_action for configuring your messages. This may be useful, for example, when you want to add default inline attachments for all messages sent out by a certain mailer class:
class Notifier < ActionMailer::Base before_action :add_inline_attachment! def welcome mail end private def add_inline_attachment! attachments.inline["footer.jpg"] = File.read('/path/to/filename.jpg') end end
Callbacks in ActionMailer are implemented using AbstractController::Callbacks, so you can define and configure callbacks in the same manner that you would use callbacks in classes that inherit from ActionController::Base.
Note that unless you have a specific reason to do so, you should prefer using before_action rather than after_action in your ActionMailer classes so that headers are parsed properly.
Previewing emails
You can preview your email templates visually by adding a mailer preview
file to the ActionMailer::Base.preview_path
. Since most emails
do something interesting with database data, you'll need to write some
scenarios to load messages with fake data:
class NotifierPreview < ActionMailer::Preview def welcome Notifier.welcome(User.first) end end
Methods must return a Mail::Message
object which can be
generated by calling the mailer method without the additional
deliver
. The location of the mailer previews directory can be
configured using the preview_path
option which has a default
of test/mailers/previews
:
config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
An overview of all previews is accessible at
http://localhost:3000/rails/mailers
on a running development
server instance.
Previews can also be intercepted in a similar manner as deliveries can be
by registering a preview interceptor that has a
previewing_email
method:
class CssInlineStyler def self.previewing_email(message) # inline CSS styles end end config.action_mailer.preview_interceptors :css_inline_styler
Note that interceptors need to be registered both with
register_interceptor
and
register_preview_interceptor
if they should operate on both
sending and previewing emails.
Configuration options
These options are specified on the class level, like
ActionMailer::Base.raise_delivery_errors = true
-
default_options
- 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 tonil
for no logging. Compatible with both Ruby's ownLogger
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. -
:openssl_verify_mode
- When using TLS, you can set how OpenSSL checks the certificate. This is really useful if you need to validate a self-signed and/or a wildcard certificate. You can use the name of an OpenSSL verify constant ('none'
,'peer'
,'client_once'
,'fail_if_no_peer_cert'
) or directly the constant (OpenSSL::SSL::VERIFY_NONE
,OpenSSL::SSL::VERIFY_PEER
, …).
-
-
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@address
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 applicationtmp/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 e.g.MyOwnDeliveryMethodClass
. 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 withdelivery_method :test
. Most useful for unit and functional testing.