This was a really good howto, which I enjoyed setting up.  However I did run into the following similar errors: 

Warning: include_once(Mail.php) [function.include-once]: failed to open stream: No such file or directory in /var/www/web/base-php4/includes/base_action.inc.php on line 29

Warning: include_once() [function.include]: Failed opening 'Mail.php' for inclusion (include_path='.:/usr/share/php') in /var/www/web/base-php4/includes/base_action.inc.php on line 29

Warning: include_once(Mail/mime.php) [function.include-once]: failed to open stream: No such file or directory in /var/www/web/base-php4/includes/base_action.inc.php on line 30

Warning: include_once() [function.include]: Failed opening 'Mail/mime.php' for inclusion (include_path='.:/usr/share/php') in /var/www/web/base-php4/includes/base_action.inc.php on line 30

Warning: Cannot modify header information - headers already sent by (output started at /var/www/web/base-php4/includes/base_action.inc.php:29) in /var/www/web/base-php4/base_common.php on line 1077

It was resolve by installing the following:

pear install Mail

pear install Mail_Mime