MailGate

MailGate is an additional delivery method for the Mail gem that lets you restrict the delivery of mail to only whitelisted emails. Ideal for staging environments where you may be using production data and do not want them to recieve emails from your mailers when you submit comments, contact forms, or anything else that may trigger mail delivery.

Add this line to your application's Gemfile:

gem 'mail_gate'

And then run:

$ bundle

Or install it yourself as:

$ gem install mail_gate

MailGate works as a standalone extension to the Mail gem or as a delivery method within Rails applications.

To configure MailGate, edit your ActionMailer configuration to use :mail_gate as the delivery method, then copy your existing settings to mail_gate_settings:

# config/environments/staging.rb
CNN::Application.configure do
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    :address        => 'smtp.sendgrid.net',
    :port           => '25',
    :authentication => :plain,
    :user_name      => ENV['SENDGRID_USERNAME'],
    :password       => ENV['SENDGRID_PASSWORD'],
    :domain         => ENV['SENDGRID_DOMAIN']
  }
end

Becomes:

# config/environments/staging.rb
CNN::Application.configure do
  config.action_mailer.delivery_method = :mail_gate
  config.action_mailer.mail_gate_settings = {
    :whitelist        => /cnn.com/,
    :delivery_method  => :smtp,
    :delivery_settings => {
      :address        => 'smtp.sendgrid.net',
      :port           => '25',
      :authentication => :plain,
      :user_name      => ENV['SENDGRID_USERNAME'],
      :password       => ENV['SENDGRID_PASSWORD'],
      :domain         => ENV['SENDGRID_DOMAIN']
    }
  }
end

When the email is sent, any emails that end up being extracted because they don't match the whitelist will be appended to the email's body so you know the intended recipients. So if you had a whitelist only for CNN.com, and you sent an email out to nytimes.com, it'd look something like:

Thanks for reading our interesting article!

Extracted Recipients: user@nytimes.com

If you dislike that behavior, you can easily turn it off by setting append_emails to false in the settings.

# config/environments/staging.rb
CNN::Application.configure do
  config.action_mailer.delivery_method = :mail_gate
  config.action_mailer.mail_gate_settings = {
    :whitelist     => /cnn.com/,
    :append_emails => false
  }
end

By default the emails send will have the same subject that they normally would. If you'd like to customize the subject to inform the reader where it was sent from you can do that with the :subject_prefix option:

# config/environments/staging.rb
CNN::Application.configure do
  config.action_mailer.delivery_method = :mail_gate
  config.action_mailer.mail_gate_settings = {
    :whitelist        => /cnn.com/,
    :subject_prefix   => '[Staging] ',
    # ...
  }
end

Now your emails that are sent will have [Staging] New comment on your article! as the subject rather than just New comment on your article!. It's entirely up to you what you may put as the prefix, be it the current deploy git SHA, or if you want to send the server's hostname that sent the mail.

Email now sent within the staging environment will extract any recipient emails that don't match the whitelist. If after being filtered there aren't any recipients left because they were filtered out, no email will be sent:

> Article.first.comments.each do |comment|
>   "Email for: #{comment.user.email}"
>   ArticleMailer.new_comment(article, comment).deliver
> end
=> Email for: john.doe@gmail.com
=> Email for: megatron@transformers.com
=> Email for: george@cnn.com
=> #<Mail::Message:70236177475420, Headers: <From: no-reply@cnn.com>, <To: george@cnn.com>, <Subject: [Staging] New comment on your article!>>

Notice only the email for george@cnn.com was delivered.

If you have a Sinatra app or just using the Mail library in your Ruby project you can still use MailGate:

require 'mail_gate'

Mail.defaults do
  delivery_method MailGate::Filter,
    :whitelist => /cnn.com/,
    :subject_prefix => '[local] ',
    :delivery_method => :file,
    :location => '/dev/null'
end

Then just deliver the email as normal:

Mail.deliver do
  to 'george@cnn.com'
  from 'no-reply@cnn.com'
  subject 'Testing MailGate'
  body 'Hi! :)'
end

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Copyright © 2012 Garrett Bjerkhoel. See LICENSE for details.