Using: 
<?php
imap_open( "{server.example.com:143}INBOX" , 'login' , 'password' );
?>

Got this error:
"Couldn't open stream {server.example.com:143}INBOX" 
Solved by adding the flag "novalidate-cert":
<?php
imap_open( "{server.example.com:143/novalidate-cert}INBOX" , 'login' , 'password' );
?>

=D