Robert Schetterer wrote, at 08/03/2009 03:40 PM: > lost mail to where ? gone universe ....*g? > the mail got rejected at last with a debug code > so the sender may take his brain to fix its problem > or try to reach you by phone , valid mailservers etc > if the sender cant fix it you can simply whitelist > them by ip or else for reject_unknown_reverse_client_hostname > mail must always be supported > using reject_unknown_reverse_client_hostname is relativly save these > spam days ,shows every day work here, the few problems a year are easy > to fix, make sure that you have very good dns resolves ( i.e use local > dns cache too) > i changed the reject code to 550, to let senders know at once about the > the problem, for fighting bots it very effective ,and dont break your head > about crying users behind if the senders cant show bounces and call it > lost mail *g
In this particular case, human senders are rarely the issue. As you suggest, they will often find ways to communicate to the recipient that there is a problem. Unfortunately, a substantial portion of the messages rejected by reject_unknown_(reverse_)client_hostname are sent by automated processes using misconfigured software or machines that bypass the more sensibly configured relays for a domain. Nobody will attempt to contact the recipient, who will often determine there is a problem when it is too late. Maintaining whitelists isn't an attractive option when there is already too much guesswork involved.
