Re: What is GreyListing

[Michael Loftis]

It's not at ll like challenge response.  Challenge response sends email tot 
he senders/humans asking them to confirm.  We're just asking systems to act 
like a noirmal mailserver during greylisting, which is 4xx, retry later. 
It won't work forever.... eventually spambots and virusbots will catch on 
and start retrying after being 4xx-ed but implementing it now makes you 
just harder than your neighbor to break into so for the time being they'll 
mostly leave you alone.


--On Tuesday, July 20, 2004 12:31 -0700 Paul Johnson <[EMAIL PROTECTED]> 
wrote:

Christian Hammers <[EMAIL PROTECTED]> writes:
Hello
On 2004-07-20 Russell Coker wrote:
(host mail3av.westend.com[212.117.79.67] said: 450 <[EMAIL PROTECTED]>:
Recipient address rejected: Greylisted for 300 seconds... (in reply to
> RCPT TO command)) [EMAIL PROTECTED]
Christian's mail server is broken.
Err, no. It's not a bug it's a feature :-) Called "greylisting".
In opposide to normal black- and white-listing here postfix has an
additional policy daemon that checks if the tripel "sending ip, from,
to" is already in the database and if not, reply with a 450 aka
"temporary(!) failure" code and take note of it.  If it's a real
mailserver and not a trojan-winXP-desktop then it will try it again in a
couple of minutes. If it does the above tripel will be whitelisted for
the next days/month/whatever.
This sounds suspiciously like (dangerously stupid) challenge-response
systems.  How does this differ?

--
Michael Loftis
Modwest Sr. Systems Administrator
Powerful, Affordable Web Hosting
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