Julien Vehent wrote:
OK, so to use STARTTLS with roundcube, the postfix server must be configured with the option smtpd_enforce_tls = yes, right ?
No, it is must not. As I see in the code, STARTTLS is called when authentication is requested (when smtp_user and smtp_pass options in Roundcube config are set) and (from Net_SMTP):
version_compare(PHP_VERSION, '5.1.0', '>=') && extension_loaded('openssl') && isset($this->_esmtp['STARTTLS']) && strncasecmp($this->host, 'ssl://', 6) != 0