This PECL extension
is not bundled with PHP.
  Additional information such as new releases,
downloads, source files, maintainer information, and a CHANGELOG, can be
located here: 
  http://pecl.php.net/package/mailparse.
 
  In order to use these functions you must compile PHP with mailparse support
  by using the --enable-mailparse configure 
  option.
 
  Windows users will enable php_mailparse.dll inside
  of php.ini in order to use these functions.
  You may download this PECL
extension DLL from the 
PHP Downloads page or at 
http://snaps.php.net/.