auth is used to specify SMTP authentication. As of edit 116, EMAILX supports two authentication methods: AUTH=PLAIN and AUTH=LOGIN. You may also specify AUTH=* (or AUTH=AUTO) to have EMAILX query the SMTP server to see which methods it supports, and to then use AUTH=LOGIN or AUTH=PLAIN according to which is supported. If both are supported, it uses AUTH=LOGIN. You can omit the auth parameter entirely if you SMTP server does not require authentication. (Many SMTP servers distinguish authorized clients by their IP address and thus don't require authentication via username and password.) If you specify the auth parameter, then you must specify the username and password (either in the configuration file or in the parameter calling list).