oh well, let me give a working version (I just put it in the MAIL ACL):
deny authenticated = *
message = Wrong sender address: $sender_address. Please
verify your configuration.
log_message = Wrong envelope sender from authenticated user
<$authenticated_id>
!verify = sender
Note that the messages are one line as I found out that Eudora Mac
only display the last line of the response...
More or less the same for relay_from_hosts (I do not have any).
Giuliano