switched from substr() to rtrim() in _write_headers() so that the last $this->newline is fully stripped when the "mail" protocol is used, regardless of whether \r, \n, or \r\n is used.
http://codeigniter.com/bug_tracker/bug/6669/
diff --git a/user_guide/changelog.html b/user_guide/changelog.html
index 65950cd..d9017d9 100644
--- a/user_guide/changelog.html
+++ b/user_guide/changelog.html
@@ -133,6 +133,7 @@
<li>Fixed bug (#6517) where Routed URI segments returned by URI::rsegment() method were incorrect for the default controller.</li>
<li>Fixed a bug (#6706) in the Security Helper where xss_clean() was using a deprecated second argument.</li>
<li>Fixed a bug in the URL helper url_title() function where trailing periods were allowed at the end of a URL.</li>
+ <li>Fixed a bug (#6669) in the Email class when CRLF's are used for the newline character with headers when used with the "mail" protocol.</li>
<li>Tweaked Typography::auto_typography() for some edge-cases.</li>
</ul>