send_by_smtp ARGS...
    Instance method.  Send message via SMTP, using Net::SMTP.  The optional ARGS
    are sent into Net::SMTP::new(): usually, these are

       MAILHOST, OPTION=>VALUE, ...

    Note that the list of recipients is taken from the "To", "Cc" and "Bcc"
    fields.

    Returns true on success, false or exception on error.