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Mick Vaites wrote: > I'm gobsmacked that you would advocate an ISP dropping a customers email > bounces but at the same time wouldn't advise a customer to do it themselves > - or am I not reading you right ? I'm not advocating dropping email at all. A 4xx is not a drop, it's a "please retry later" and as such is a perfectly valid response to a deliverable message. > Issuing a 4xx puts the responsibility back on the originator of the message > to resend the message which may not happen for some time. Whereas the backup > MX could have more friendly rules for it's customers on resending - and thus > reducing the delay in getting the email to the person. It could, but it's a small could, and, unless the backup MX can be authoritative about its mail delivery, the downside far exceeds the benefits. > I take your point about Spammers assuming they are the ones actually sending > them mail directly to the MX's. My understanding however is that more and > more spam gets sent via Bot's. Which uses a customers ISP's outbound smtp > server. We're seeing more and more customers being hit this way. I'm less than convinced that as a provider of outbound relaying services it's sensible to trust your users not to originate spam or messages from random sender addresses either. Plenty of people spam-filter outbound messages and rate-limit users (amongst other things) for precisely that reason. However, if the intended recipients of such spam messages reject them outright at the receiving MX rather than silently dropping them on the floor (or, to a certain extent, just generate a 4xx if they can't guarantee delivery), then the mail provider is the one whose mail queues fill up (and potentially who generates backscatter) and it becomes their problem. That's the right place for the problem to be, because they're the ones transmitting the spam for their spam-generating customer, and they should bear the cost that entails. > Reference your comments on secondary MX's -- since the advent of ADSL more > and more customers are using us as backup MX's or Smart hosts. Principally > because the RBL's are picking on the ADSL IP space more and more. I'm sure there are those who would argue that it's those netblocks assigned to ADSL customers where the originator can't be definitively identified that generally end up in the RBLs and that there isn't usually a problem with well-maintained static assignments (where that includes a responsive abuse-management function). I can't see that there's a particularly compelling reason to allow users with dynamic address assignments to deliver email directly, I have to admit. James -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html