diff --git a/actionmailer/lib/action_mailer/mail_helper.rb b/actionmailer/lib/action_mailer/mail_helper.rb
index ec84256491..892eb2472f 100644
--- a/actionmailer/lib/action_mailer/mail_helper.rb
+++ b/actionmailer/lib/action_mailer/mail_helper.rb
@@ -1,4 +1,7 @@
 module ActionMailer
+  # Provides helper methods for ActionMailer::Base that can be used for easily
+  # formatting messages, accessing mailer or message instances, and the
+  # attachments list.
   module MailHelper
     # Take the text and format it, indented two spaces for each line, and
     # wrapped at 72 columns.