How To: Use custom mailer

To use a custom mailer, create a class that extends Devise::Mailer, like this:

class MyMailer < Devise::Mailer   
  helper :application # gives access to all helpers defined within `application_helper`.
  include Devise::Controllers::UrlHelpers # Optional. eg. `confirmation_url`
  default template_path: 'devise/mailer' # to make sure that your mailer uses the devise views
  # If there is an object in your application that returns a contact email, you can use it as follows
  # Note that Devise passes a Devise::Mailer object to your proc, hence the parameter throwaway (*).
  default from: ->(*) { Class.instance.email_address }
end

Then, in your config/initializers/devise.rb, set config.mailer to "MyMailer". Note that this overrides the mailer used for all devise modules.

You may now use your MyMailer in the same way as any other mailer. In case you want to override specific mails to add extra headers, you can do so by simply overriding the method and calling super at the end of your custom method, to trigger Devise's default behavior.

For instance, we can add a new header for the confirmation_instructions e-mail as follows:

def confirmation_instructions(record, token, opts={})
  headers["Custom-header"] = "Bar"
  super
end

You can also override any of the basic headers (from, reply_to, etc) by manually setting the options hash:

def confirmation_instructions(record, token, opts={})
  headers["Custom-header"] = "Bar"
  opts[:from] = 'my_custom_from@domain.com'
  opts[:reply_to] = 'my_custom_from@domain.com'
  super
end

In order to get preview (if User is your devise model name):

# test/mailers/previews/my_mailer_preview.rb
# Preview all emails at http://localhost:3000/rails/mailers/my_mailer

class MyMailerPreview < ActionMailer::Preview

  def confirmation_instructions
    MyMailer.confirmation_instructions(User.first, "faketoken", {})
  end

  def reset_password_instructions
    MyMailer.reset_password_instructions(User.first, "faketoken", {})
  end

  def unlock_instructions
    MyMailer.unlock_instructions(User.first, "faketoken", {})
  end
end

In order to control which queue name the mailer queues up new email, add the following method to your class (MyMailer, above):

def deliver_later
   Devise::Mailer.delay(queue: 'my_queue').send(...)
end