On Fri, Jul 3, 2009 at 7:55 AM, Barney Desmond<barneydesm...@gmail.com> wrote: > 2009/7/3 Gábor Lénárt <l...@lgb.hu>: >> Hei, >> >> Recently I am thinking of reimplementing our MX servers. Of course rcpt >> check is a must, also I should not generate NDRs later, I should only accept > <snip> > > Huh? > > This is all very standard behaviour for an MTA. Recipient checking is > a very common task for most Postfix users. Regardless of what you > expect or want, SMTP is a store-and-forward protocol - queues are a > strong component for an MTA. > > You say you don't want to accept mail unless you're certain that the > backend can accept it, but the only way to know is to try. If it > succeeds then you might as well take it, you've already succeeded. In > any case, this amounts to simply collapsing all the layers of your > mail system, from receipt to storage. This of course depends on how > you expect to implement the systems, which you've not described. >
Right, NDRs are not always bad. Generating millions of the for dumb reasons (in response to dictionary attacks for example) is bad. Sending one when there is an unforeseeable problem such as those you mention is really ok and a good thing. They serve an important purpose.
