SECURE

SECURE may optionally be used to specify the type of secure connection to establish with the SMTP server. The options are TLS (establish an SSL/TLS encrypted connection immediately, typically at port 465), STARTTLS (start with an unencrypted connection and then upgrade to TLS using the STARTTLS SMTP command), or NONE (unencrypted connection). If SECURE is not specified, the option defaults to NONE. Note that changing the SECURE option typically requires changing the port (see server above).