title: Rails3 Global Header Inclusion
body: <p>I've got a few ActionMailer classes that send out a number of emails....  I want to globally include a header across every single email sent from this Rails app:</p>
  
  <p>Here is a method with the header manually included:</p>
  
  <pre><code>class GeneralNotification &lt; ActionMailer::Base
  
      def test_email(emails)
          subject "Welcome to my email!"
          recipients "somebody@somewhere.com"
          from "chad@awesome.com"
  
          headers(
              "X-SMTPAPI" =&gt; '{"category": "Test Category"}'
          )
      end
  
  end
  </code></pre>
  
  <p>I want that X-SMTPAPI header globally included without modifying every mailer method..</p>
  
  <p>What's the best way to do this?</p>
  
  <p>Thanks!</p>
  
  <p>Chad</p>