The Secure property determines if a secure connection is
established to the server. The default value for this property is
False, which specifies that a standard connection to the server is
used. To establish a secure connection, the application must set this
property value to True prior to calling the SendMessage method.
This property is only used when sending a message through a relay
server using the SMTP service. Messages that are sent directly to the
wireless service provider's gateway do not use authentication and are
not secure, regardless of the value of this property.