PHP imap_open to exchange 2010 : Unable to negotiate TLS with this server

[k_romych]

Hi
I am getting " Unable to negotiate TLS with this server" when trying to connect to exchange 2010 from imap_open() in PHP script. PHP ver is 5.2.17. I can connect to other mail servers but this one. IMAP on the server is set to "Secure logon. A TLS connection is required for the client to authenticate to the server" and is accessible from outlook or telnet on port 143.

And thats a connection line
$mbox = imap_open("{10.0.10.12:143/imap4/tls/novalidate-cert/debug}INBOX", "username", "pass", OP_DEBUG);
I have tried it with different options, triple checked the details.
Thanks