en.yml

en:  
  emails:
    signup_notification:
      subject: "Your account on WEBSITE has been set up"
      body: "Hi {{username}},

A new account has been set up for you on WEBSITE.

Here is your link to get started:
  
{{url}}

Regards,

WEBSITE
"

mail.erb

<%= t("emails.#{message}.body") %>

mailer.rb

class Mailer < ActionMailer::Base

  def email(message,user,params = {})
    subject I18n.t("emails.#{message}.subject")
    body params.merge({:message => message, :params => params})
  end

  protected
  
  def setup_email(user)
    recipients "#{user.email}"
    from 'WEBSITE <admin@website.net>'
    @sent_on = Time.now
    @body[:user] = user
  end
end

mailer_spec.rb

require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')

describe Mailer do
  before(:each) do
    @user = mock_model(User, :email => 'test@test.com', :login => 'test')
    @mailer = Mailer.create_email('signup_notification', @user, {:username => @user.login, :url => 'test.com'})
  end
  
  it "should load up the translation" do
    @mailer.subject.should match(/WEBSITE/)
  end
  
  it "should have a body" do
    @mailer.body.should match(/test.com/)
  end
end