anchor.diff:      error.
   
   handle_RCPT(_From, State=#state{auth_user=undefined}) ->
  +    rabbit_log:error("SMTP authentication is required~n"),
       {error, ?AUTH_REQUIRED, State};
   handle_RCPT(_To, State) ->
       % you can accept or reject RCPT TO addesses here, one per call
  
positive.code:     error.
  
  handle_DATA(_From, _To, _Data, #state{auth_user=undefined} = State) ->
      {error, ?AUTH_REQUIRED, State};
  handle_DATA(_From, _To, <<>>, State) ->
      {error, "552 Message too small", State};
  
negative.code:     end.
  
  handle_MAIL(_From, State=#state{auth_user=undefined}) ->
      rabbit_log:error("SMTP authentication is required~n"),
      {error, ?AUTH_REQUIRED, State};
  handle_MAIL(_From, State) ->
      % you can accept or reject the FROM address here
  