On 2006-03-30, Peter Bowyer <[EMAIL PROTECTED]> wrote: >> >> But when MTA(n) rejects a message that MTA(n-1) is trying to relay, >> >> MTA(n-1) has to bounce it, right? >> > >> > MTA(n-1) shouldn't accept messages to invalid recipients in the first >> > place. If it has no direct knowledge of valid recipients, it should do >> > callouts. >> >> I understood those weren't reliable because (there may be other >> reasons?) in many cases MTA(n) is configured not to give out that >> information because spammers could use it. > > The usual use case here is a 'border' MTA receiving mail for a known > list of domains and forwarding to inner mailbox servers. In those > controlled circumstances, recipient callouts are just fine. They > shouldn't be used to indiscriminate destinations - but an MTA > shouldn't be relaying for indiscriminate destinations either.
I'm thinking of MTA(n-1) as a department's outgoinggmailhub or ISP's smarthost. It's usually configured to accept anything from within the IP range it's supposed to cover, and use DNS MX to pick MTA(n) for non-local recipients. That's the sort of situation in which I was under the impression that MTA(n-1) would often be unable to get the recipient-verify callout information. Have I got this wrong? -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
