Server environment: Windows 2003 Server R2, IIS 6, PHP 5.2.5 in ISAPI mode with POP3 support ENABLED
wp-mail.php generates a 500 Internal Server Error when attempting to require_once class-pop3.php
running class-pop3.php directly returns same error message
editing class-pop3.php's class name from POP3 to anything else eliminates the error. conclusion is that the class name "masks" the class name already in use in the core PHP code (y/n? not an experts guess).
other functionality needs the PHP 5 setting for POP3 support to be enabled so turning that off isn't a viable solution. any ideas?