How to solve the authentication issue using PHP open_imap() function

I tried to connect to aruba mail server using PHP open_imap() function

Here is my code:

    $host = 'imap.xxx.com';   
    $port = 993;
    $username   = "[email protected]";   
    $password   = "abc";   

    $imapConnection = imap_open("{" . $host . ":" . $port . "/imap/ssl/novalidate-cert/notls/norsh}INBOX", $username, $password);

    echo $imapConnection . "<br><br>";

    echo date("d/m/Y h:m:s", time()) . "<br><br>";

    var_dump(imap_errors());

I did not find any way out using aruba mail server!

output:

array(3) {
  [0]=> string(81) "Retrying PLAIN authentication after [AUTHENTICATIONFAILED] Authentication failed."
  [1]=> string(81) "Retrying PLAIN authentication after [AUTHENTICATIONFAILED] Authentication failed."
  [2]=> string(82) "Can not authenticate to IMAP server: [AUTHENTICATIONFAILED] Authentication failed."
}