The Horde_Mail library is a fork of the PEAR Mail library that provides additional functionality, including (but not limited to): * Allows a stream to be passed in. * Allows raw headertext to be used in the outgoing messages (required for things like message redirection pursuant to RFC 5322 [3.6.6]). * Native PHP 5 code. * PHPUnit test suite. * Provides more comprehensive sendmail error messages. * Uses Exceptions instead of PEAR_Errors. WWW: http://pear.horde.org