commit 819c4767cea5c8523938b27a29e48a7ab82b503d
Author: kennyj <kennyj@gmail.com>
Date:   Fri Nov 30 00:22:08 2012 +0900

    Fix build on Ruby18. We should specify endian for UTF16/32.

diff --git a/lib/mail/version_specific/ruby_1_8.rb b/lib/mail/version_specific/ruby_1_8.rb
index cb2bae6..f7c65bb 100644
--- a/lib/mail/version_specific/ruby_1_8.rb
+++ b/lib/mail/version_specific/ruby_1_8.rb
@@ -107,6 +107,10 @@ module Mail
       case encoding.upcase
       when 'UTF8'
         'UTF-8'
+      when 'UTF16', 'UTF-16'
+        'UTF-16BE'
+      when 'UTF32', 'UTF-32'
+        'UTF-32BE'
       else
         encoding
       end