An AuthMethodEnum expression that indicates the authentication method.
By default, the control uses no authentication method. Use
the AuthMethod property to specifies the authentication method. The "AUTH
LOGIN" and "AUTH PLAIN" supported. The authentication method
depends on the SMTP server you are using. Use the LogonUser
and LogonPassword properties if the authentication
method is
AuthLogin or AuthPlain. The RFC 2554
describes the SMTP Authentication.
