It means exactly that. It's not a problem with the script and there's nothing to solve. It is simply that PHP must be compiled with IMAP support if you want this to work.
http://www.php.net/manual/en/book.imap.php(http://www.php.net/manual/en/book.imap.php)
If you're on a shared host, contact your hosting provider and tell them you need this functionality. If not, see the link above.
The library is a bit incorrectly named, since it's used for both IMAP and POP3.... but none the less, that's what you need.
:)
