There is no config.action_mailer.default_charset method for Rails 3

railties/guides/source/configuring.textile

@@ -187,8 +187,6 @@ There are a number of settings available on +config.action_mailer+:
 
 * +config.action_mailer.perform_deliveries+ specifies whether mail will actually be delivered. By default this is +true+; it can be convenient to set it to +false+ for testing.
 
-* +config.action_mailer.default_charset+ tells Action Mailer which character set to use for the body and for encoding the subject. It defaults to +utf-8+.
-
 * +config.action_mailer.default_content_type+ specifies the default content type used for the main part of the message. It defaults to "text/plain"
 
 * +config.action_mailer.default_mime_version+ is the default MIME version for the message. It defaults to +1.0+.