warning: fsockopen(): no SSL support in this build

I'm trying to use SSL for sending SMTP mail, but I see the "No SSL support in this build" message.

I'm doing this on Redhat EL and php is compiled '--with-openssl' as expected. In fact, I'm using PHPmailer successfully on the same server and PHP build with SSL - in a non-drupal script. I'm therefore certain that SSL availability on PHP is not the problem.

Any ideas?

Thanks