This method should be called directly after the construction of this
object.
If the server is waiting for the authentication process to respond, the
connection with the IMAP server will be closed, and false is returned,
and it is the application's task to reconnect and reauthenticate.
Example of creating an IMAP transport and authenticating:
replace with your IMAP server address
$imap = new ezcMailImapTransport( 'imap.example.com' );
replace the values with your username and password for the IMAP server
$imap->authenticate( 'username', 'password' );