Autor: Steve Brown Data: A: exim-users Assumpte: Re: [exim] Callouts, NULL DSN
So basically it seems that one could consider a very loose interpretation of
the RFC's "everything should be accepted with a null DSN" appropriate, while
another could consider a stricter interpretation of "you only have to accept
null DSN to accommodate for mail originating from your server" appropriate.
From what I have gathered reading various discussions and on this list, it
seems that the need for a stricter interpretation has gained favor and
general acceptance due to the actions of malevolent parties and the need to
deal with those situations.