On Thu, 2008-03-27 at 21:43 -0700, Craig White wrote: > On Fri, 2008-03-28 at 12:45 +0900, John Summerfield wrote: > > Craig White wrote: > > > > > > > > > > > You are correct of course, that nowhere does it state that sender MUST attempt to re-deliver. I do wonder if you would find an SMTP server that by default didn't attempt re-delivery on temporary failures to be acceptable. It MUST be configurable - that's it. > > > > > > Okay, so Tim wasn't sure, but now we agree retrying, while it might be > > good practice isn't essential. > ---- > not essential in that the RFC does not say MUST > > essential only if the intent was to surely deliver e-mail > ---- > > > > I've just done a "host -t mx" for several companies. Most have four mail > > exchangers, one had a dozen. While those are for incoming email, it's > > likely that they generally have a similar number for outgoing email. > > Without information, I assume that to be so. In many cases they will be > > the same machine. > > > > I don't know what their retrying policies are, but I can imagine that > > retrying might involve an attempt by each of several machines, each > > getting a 4XY response. > > > > It might be a lengthy delay, it might result in email getting returned > > to sender. > > > > Tim is right in his belief that greylisting can cause delivery problems. > > You don't have to think it's as big a problem as he does, but I don't > > criticise him for seeing it as a risk he doesn't want to take. > > > > > > Here is one list of recommended delays between retries: > > http://www.mailenable.com/Help/Files/smtpdelivery.htm > > > > > > The use of fake mx records suggested here looks enticing: > > http://wiki.apache.org/spamassassin/OtherTricks > > > > I discontinued using a second mx because it seemed only to receive spam, > > and senders _should_ retry if I'm not listening. > ---- > the 'fake mx records' suggests the use of Temp Fail codes on the highest > fake MX > > *** sigh *** > > I guess that if you think that NOT running greylisting means you get > delivery 100% of the time and running greylisting means that you only > get delivery 99.99% of the time (referring of course only to legitimate, > non-UBE e-mail) then you must be be indulging in willful sabotage and > not worthy of hire (Tim's words). > > Temp Fail codes exist, are stipulated and understood by RFC and by ALL > SMTP servers. > > The alternative is to run user level spam filtering. I submit that it is > for most businesses, a stupid, wasteful, inefficient plan but I > acknowledge that ISP servers cannot necessarily adopt these aggressive > tactics. > > Craig > But is 99.99% delivery sufficient? I receive more than 150 emails per day (ones that I am interested in), and every few days I need to receive certain emails about customer relations and ongoing projects. 99.99 percent means I would miss one every 66 days. If the one that I miss cost me a contract, it might not matter whether I received the rest or not. Currently I have to parse through the junk mail locally and remotely about once a week. the ISP junk folder often has more than 1200 emails in it. THe local one about 30. This adds about 1/2 day of overhead every week to recapture what should have come through. Personally I think the world needs to eliminate spam, or at least make every effort to seriously reduce it. Regards, Les H
