if anonymous(_at_)[] doesn't quite work, there are similar alternatives
worth
considering. among them are: anonymous(_at_)[0(_dot_)0(_dot_)0(_dot_)0],
anonymous(_at_)[127(_dot_)0(_dot_)0(_dot_)1],
anonymous(_at_)[127(_dot_)255(_dot_)255(_dot_)255], anonymous(_at_)[::0], and
anonymous(_at_)[::1].
These might be OK in the message header. In the envelope they are
likely
to be rejected as invalid, because many sites put restrictions on the
use
of domain literals, and checks on envelope addresses tend to be more
thorough. In addition to that, many sites reject domains that do not
refer
to globally routable addresses.
exactly so. in the envelope I recommend that MAIL FROM:<> be used. a
lot of MTAs reject it these days, but they are clearly broken.