I don't see the emails from the list.

[Kenneth Brody]

Quoting Jay R. Ashworth (Sat, 29 Sep 2007 20:33:20 -0400):

> On Wed, Sep 26, 2007 at 09:46:50AM -0700, Bill Campbell wrote:
>> Some ISPs are using ``grey listing'', a process in which messages
>> are initially rejected with a 400 series SMTP message, later to
>> be accepted.  The idea is that legitimate MTAs (Mail Transport
>> Agents) will retry later while spammer's malware probably won't.
>> This may result in delays sending messages to these ISPs.
>
> The definition of greylisting that I have seen (and which I use, and
> which doesn't work all that well anymore) is to put a higher-priority
> MX pointed at a machine that doesn't accept incoming TCP/25 -- or
> better yet, behind a firewall which ignores it.

I haven't seen that definition before.  What I've seen is the same
as Bill's.  The basic idea is that it's somewhere between blacklisting
(refuse everything from it outright) and whitelisting (accept everything
from it without filtering).  Hence the name "greylisting".

The first time the combination of IP address and either "from" or "to"
(I forget which) is seen, it replies with an SMTP "try again later"
notice.  Spammers probably won't queue and try again, whereas legitimate
ISPs will.

The result is a slight delay the first time someone sends an e-mail to
someone else.  Further e-mails go through without the delay.  (Though
they will still get the usual filtering at that point.)

Wouldn't your version delay all incoming e-mail?

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