Backscatterer.org, another antisocial and technically stupid blocklist - idiots at work. Once again, an antisocial and stupid wannabe expert tries to redefine the Internet according to his opinion. This time it's against sender callouts - a technique that helps quite well against spam because addresses can be checked for validity with it. And all with minimal effort for the mail servers - a small sequence of HELO, MAIL FROM and RCPT TO (which would come later in any case with every bounce) and then directly a QUIT - so no mail in the queue, but only a check based on SMTP. The argument that he has to deal with the verifiers in addition to the bounces is nonsense - because if the verify does not come, the bounces come from these failed mails, because not only the senders are in a much larger part garbage, also the recipients (of the mail traffic that we push, only the smallest part is actually valid in terms of emails). Turning off the verification only leads to a greater occurrence of bounces - and they are expensive, because they go into the mail queue, while the verifies do not go there. The argument about loops is also stupid - correct callbacks happen with an empty envelope-from, so the other server knows immediately that it does not need to perform verification (in principle, a bounce delivery is simulated, and loops are also prevented by the empty envelope-from). The purpose of the verification is to answer the question of whether you could send a bounce to the technical sender in case of doubt. If you can't do that, you can't accept a mail if you can't directly guarantee to check all the factors up front. This is a completely legitimate procedure and absolutely conformant with the RFCs. The operators of this list are only surpassed in stupidity by the mail administrators who enter such a list into their server as a blocklist. How stupid do you have to be for that? I know how stupid, because since today I know the first server that does this ...