MultiMail: Easily switch email APIs

Many providers offer APIs to send, receive, and parse email. MultiMail lets you easily switch between these APIs, and integrates tightly with the Mail gem.

Cloudmailin: Example
Mailgun: Example
Mandrill: Example
Postmark: Example
SendGrid: Example
MTA like Postfix or qmail: Example

Usage

Incoming

require 'multi_mail'

# Create an object to consume the webhook data.
service = MultiMail::Receiver.new(:provider => 'mandrill')

# Process the webhook data, whether it's raw POST data, a params hash, a Rack request, etc.
messages = service.process(data)

messages will be an array of Mail::Message instances.

Any non-standard parameters provided by an API are added to each message as an instance variable. For example, Mailgun provides stripped-text, which is the message body without quoted parts or signature block. You can access it as message.stripped_text. The instance variable is the non-standard parameter in lowercase with underscores instead of hyphens.

Outgoing

With MultiMail, you send a message the same way you do with the Mail gem. Just set delivery_method:

require 'multi_mail'

message = Mail.new do
  delivery_method MultiMail::Sender::Postmark, :api_key => 'your-api-key'

  to 'user@wookiecookies.com'
  from 'Chewbacca <chewy@wookiecookies.com>'
  subject 'How About Some Cookies?'

  text_part do
    body 'I am just some plain text!'
  end

  html_part do
    content_type 'text/html; charset=UTF-8'
    body '<html><body><h1>I am a header</h1><p>And I am a paragraph</p></body></html>'
  end
end

message.deliver

Alternatively, instead of setting delivery_method during initialization, you can set it before delivery:

message = Mail.new do
  to 'user@wookiecookies.com'
  from 'Chewbacca <chewy@wookiecookies.com>'
  subject 'How About Some Cookies?'

  text_part do
    body 'I am just some plain text!'
  end

  html_part do
    content_type 'text/html; charset=UTF-8'
    body '<html><body><h1>I am a header</h1><p>And I am a paragraph</p></body></html>'
  end
end

message.delivery_method MultiMail::Sender::Postmark, :api_key => 'your-api-key'

message.deliver

Or, if you are sending many messages, you can set a default delivery_method for all messages:

Mail.defaults do
  delivery_method MultiMail::Sender::Postmark, :api_key => 'your-api-key'
end

ActionMailer

First, add the delivery method to ActionMailer:

ActionMailer::Base.add_delivery_method :mandrill, MultiMail::Sender::Mandrill, :api_key => 'your-api-key'

Set the default delivery method for all ActionMailer classes in config/environments/<ENV>.rb:

config.action_mailer.delivery_method = :mandrill

Or, set the delivery method in an ActionMailer class:

class UserMailer < ActionMailer::Base
  default :delivery_method => :mandrill
end

Or, set the delivery method in an ActionMailer method:

class UserMailer < ActionMailer::Base
  def welcome_email(user)
    mail({
      :to => user.email,
      :subject => 'Welcome to My Awesome Site',
      :delivery_method => :mandrill,
    })
  end
end

Set the delivery method's default options for all ActionMailer classes in config/environments/<ENV>.rb:

config.action_mailer.mandrill_settings = {:api_key => 'your-api-key', :template_name => 'default'}

Or, set the delivery method's options in an ActionMailer method:

class UserMailer < ActionMailer::Base
  def welcome_email(mail)
    mail({
      :to => user.email,
      :subject => 'Welcome to My Awesome Site',
      :delivery_method_options => {:template_name => 'default'},
    })
  end
end

Or, set the delivery method's options in an ActionMailer action:

class UserMailer < ActionMailer::Base
  before_action :set_delivery_method_options

  ...

  private

    def set_delivery_method_options
      mail.delivery_method.template_name = 'default'
    end
end

Tagging

Mailgun, Mandrill and Postmark allow you to tag messages in order to accumulate statistics by tag, which will be accessible through their user interface:

require 'multi_mail'

message = Mail.new do
  delivery_method MultiMail::Sender::Mandrill, :api_key => 'your-api-key'

  tag 'signup'
  tag 'promotion'

  ...
end

message.deliver

Mailgun accepts at most 3 tags and Postmark at most one tag.

Track opens and clicks

Mailgun, Mandrill and Postmark allow you to set open tracking, and Mailgun and Mandrill allow you to set click tracking on a per-message basis:

require 'multi_mail'

message = Mail.new do
  delivery_method MultiMail::Sender::Mailgun,
                  :api_key => 'your-api-key',
                  :domain => 'your-domain.mailgun.org',
                  :track => {
                    :opens => true,
                    :clicks => false,
                  }
  ...
end

message.deliver

Mailgun and Mandrill track whether a recipient has clicked a link in a message by rewriting its URL. If want to rewrite URLs in HTML parts only (leaving URLs as-is in text parts) use :clicks => 'htmlonly' if you are using Mailgun; if you are using Mandrill, do not set :clicks and instead configure click tracking globally in your Mandrill sending options.

Inspect the API response

Pass :return_response => true to delivery_method and use the deliver! method to send the message:

message = Mail.new do
  delivery_method MultiMail::Sender::Postmark, :api_key => 'your-api-key', :return_response => true
  ...
end

message.deliver!

Note that the deliver! method ignores Mail's perform_deliveries and raise_delivery_errors flags.

Cloudmailin

Incoming

service = MultiMail::Receiver.new({
  :provider => 'cloudmailin',
})

The default HTTP POST format is raw. Add a :http_post_format option to change the HTTP POST format, with possible values of "multipart", "json" or "raw" (default):

service = MultiMail::Receiver.new({
  :provider => 'cloudmailin',
  :http_post_format => 'raw',
})

If you are using an Amazon S3 attachment store, add a :attachment_store => true option. You must set the attachment store's permission setting to "Public Read".

service = MultiMail::Receiver.new({
  :provider => 'cloudmailin',
  :http_post_format => 'multipart',
  :attachment_store => true,
})

See Cloudmailin's documentation for these additional parameters provided by the API:

reply_plain
spf-result

Mailgun

Incoming

service = MultiMail::Receiver.new({
  :provider => 'mailgun',
})

To check that a request originates from Mailgun, add a :mailgun_api_key option:

service = MultiMail::Receiver.new({
  :provider => 'mailgun',
  :mailgun_api_key => 'key-xxxxxxxxxxxxxxxxxxxxxxx-x-xxxxxx',
})

If you are using the raw MIME format, add a :http_post_format => 'raw' option:

service = MultiMail::Receiver.new({
  :provider => 'mailgun',
  :http_post_format => 'raw',
})

See Mailgun's documentation for these additional parameters provided by the API:

stripped-text
stripped-signature
stripped-html
content-id-map

Outgoing

Mail.deliver do
  delivery_method MultiMail::Sender::Mailgun, :api_key => 'your-api-key', :domain => 'your-domain.mailgun.org'
  
  to _to_
  from _from_
  subject _subject_

  text_part do
    body _text_
  end

  html_part do
    content_type 'text/html; charset=UTF-8'
    body _html_
  end
end

You may pass additional arguments to delivery_method to use Mailgun-specific features (see docs):

o:campaign
o:dkim
o:deliverytime
o:testmode
o:tracking
v:

Mail.deliver do
  delivery_method MultiMail::Sender::Mailgun, :api_key => 'your-api-key', :domain => 'your-domain.mailgun.org',
                  :o:campaign => 'campaign', :o:dkim => 'yes (or no)',...
  ...
end

Mandrill

Incoming

service = MultiMail::Receiver.new({
  :provider => 'mandrill',
})

To check that a request originates from Mandrill, add :mandrill_webhook_key and :mandrill_webhook_url options (you can get your webhook key from Mandrill's Webhooks Settings):

service = MultiMail::Receiver.new({
  :provider => 'mandrill',
  :mandrill_webhook_key => 'xxxxxxxxxxxxxxxxxxxxxx',
  :mandrill_webhook_url => 'http://example.com/post',
})

The default SpamAssassin score needed to flag an email as spam is 5. Add a :spamassassin_threshold option to increase or decrease it:

service = MultiMail::Receiver.new({
  :provider => 'mandrill',
  :spamassassin_threshold => 4.5,
})

See Mandrill's documentation for these additional parameters provided by the API:

ts
email
dkim-signed
dkim-valid
spam_report-score
spf-result

Outgoing

Mail.deliver do
  delivery_method MultiMail::Sender::Mandrill, :api_key => 'your-api-key'
  
  to _to_
  from _from_email_ + _from_name_
  subject _subject_

  text_part do
    body _text_
  end

  html_part do
    content_type 'text/html; charset=UTF-8'
    body _html_
  end
end

You may pass additional arguments to delivery_method to use Mandrill-specific features (see docs):

important
auto_text and auto_html
inline_css
url_strip_qs
preserve_recipients
bcc_address
tracking_domain and signing_domain
merge, global_merge_vars and merge_vars
google_analytics_domains and google_analytics_campaign
metadata and recipient_metadata
async
ip_pool
send_at
template_name
template_content

Mail.deliver do
  delivery_method MultiMail::Sender::Mandrill, :api_key => 'your-api-key',
                  :async => true, :ip_pool => 'main_pool', ...
  ...
end

Postmark

Incoming

service = MultiMail::Receiver.new({
  :provider => 'postmark',
})

See Postmark's documentation for these additional parameters provided by the API:

MailboxHash
Tag

Outgoing

Mail.deliver do
  delivery_method MultiMail::Sender::Postmark, :api_key => 'your-api-key'
  
  to _To_
  from _From_
  subject _Subject_

  text_part do
    body _TextBody_
  end

  html_part do
    content_type 'text/html; charset=UTF-8'
    body _HtmlBody_
  end
end

SendGrid

Incoming

service = MultiMail::Receiver.new({
  :provider => 'sendgrid',
})

The default SpamAssassin score needed to flag an email as spam is 5. Add a :spamassassin_threshold option to increase or decrease it:

service = MultiMail::Receiver.new({
  :provider => 'sendgrid',
  :spamassassin_threshold => 4.5,
})

See SendGrid's documentation for these additional parameters provided by the API:

dkim
SPF
spam_report
spam_score

Outgoing

Mail.deliver do
  delivery_method MultiMail::Sender::SendGrid, :api_user => 'username', :api_key => 'password'
  
  to _to_
  from _from_ + _fromname_
  subject _subject_

  text_part do
    body _text_
  end

  html_part do
    content_type 'text/html; charset=UTF-8'
    body _html_
  end
end

You may also pass a x-smtpapi option to delivery_method (see SendGrid's documentation).

Mail.deliver do
  delivery_method MultiMail::Sender::SendGrid, :api_user => 'username', :api_key => 'password',
                  :x-smtpapi => '{ "some_json" : "with_some_data" }'
  ...
end

MTA

Incoming

If you are switching from an email API to Postfix or qmail, the simplest option is to continue sending messages to your application's webhook URL.

Your Postfix configuration may look like:

# /etc/postfix/virtual
incoming@myapp.com myappalias

# /etc/mail/aliases
myappalias: "| multi_mail_post --secret my-secret-string http://www.myapp.com/post"

Your qmail configuration may look like:

# /var/qmail/mailnames/myapp.com/.qmail-incoming
| multi_mail_post --secret my-secret-string http://www.myapp.com/post

In your application, you would use the simple provider:

service = MultiMail::Receiver.new({
  :provider => 'simple',
  :secret => 'my-secret-string',
})

It's recommended to use a secret key, to ensure that the requests are sent by Postfix and qmail and not by other sources on the internet.

This gem re-uses code from fog, released under the MIT license.

multi_mail

Development

Runtime

MultiMail: Easily switch email APIs

Usage

Incoming

Outgoing

ActionMailer

Tagging

Track opens and clicks

Inspect the API response

Cloudmailin

Incoming

Mailgun

Incoming

Outgoing

Mandrill

Incoming

Outgoing

Postmark

Incoming

Outgoing

SendGrid

Incoming

Outgoing

MTA

Incoming