On Fri, 8 Feb 2008, Stuart Henderson wrote: >On 2008/02/08 11:35, Dave Anderson wrote: >> On Fri, 8 Feb 2008, Peter N. M. Hansteen wrote: >> >> >Raimo Niskanen <[EMAIL PROTECTED]> writes: >> > >> >> If a backscatter gets through to sendmail, and it is to an invalid >> >> user, what is the proper thing for sendmail to do? My sendmail >> >> most probably does the default, which I guess is to bounce the mail. >> > >> >yes, if you receive a message intended for a non-existing user, you >> >most likely bounce with 'unknown user' or the equivalent. it's the >> >other end, where spam apparently gets delivered, that's making more >> >noise than necessary by bouncing messages that should have simply been >> >forwarded to /dev/null instead. >> >> While I agree with most of what you're saying, quietly dropping messages >> identified as spam is _not_ the best way of handling them -- since it's >> rarely possible to be 100% certain that a message really is spam, and >> it's harmful to not notify the sender that a legitimate message has not >> been delivered. > >If you do this, and people forward mail to your machine, or you list >a backup MX which accepts some spam that your machine doesn't, your >policy results in backscatter to the envelope sender address.
As I stated in the part of my message that you didn't quote, it's not a 100% solution -- but it would drastically reduce the amount of backscatter if everyone did it. And, IMO, some backscatter is a much less serious problem than _any_ legitimate message disappearing without a trace. >There's no right answer... There's no _perfect_ answer (short of a complete redesign of SMTP), but there are certainly ones which improve on the current state of affairs. Dave -- Dave Anderson <[EMAIL PROTECTED]>