Re: [exim] conducive.org

David Woodhouse wrote:
> On Wed, 2006-10-18 at 18:43 +0800, W B Hacker wrote:
>> As we have no such user as:
>> gandalf.llorien.org-1159383911-testing@???
>> This was neither....
>
> That's done in order to reduce the load on the server we call out to.
>
> While we happen to be connected after a successful callout, we try a
> second RCPT with an address which is fairly sure to fail. If _that_ is
> accepted, we assume that the server in question will accept _all_
> callouts, so we don't bother to make any more (at least until the cache
> expires).
>

That's indeed the purpose of the random callout: reduce load on some
remote servers.
Furthermore, if you blacklist an IP just because it sends _ONE_ mail to
a non existing user, you will rapidly end up blacklisting many people
who should not have been. And if your error message states this is
because the sender is not RFC compliant, while it in fact is, it is even
worse.