function imap_open access cyrus-imapd 2.2.3 error--------user notfound!

[Hartt]

hi,all

I have written a php scripts to test my mail server which built with
Cyrus-imapd 2.2.3 OpenLDAP Postfix.

<?php
if(!imap_open("{MailServerDomain:143/imap/notls}INBOX","username","password"))
echo "error is ".imap_last_error()."\n";
else
echo "successful";
?>
But the browser told me that:
Warning: imap_open(): Couldn't open stream {localhost:143/notls}INBOX in
/var/www/hartt.realss/egroupware/dawnlinux.php on line 2
error is Can not authenticate to IMAP server: user not found

But i test this script with another Mailserver which built with the some
version softwares but the cyrus-imapd 2.1.15.

And it could response that "successful".

And all the two server could access by Mozilla-Thunderbird and could
send and receive messages correctly.

what wrong with it?

Thank you in advance!