[Mimedefang] Greylisting

[Steffen Kaiser]

On Wed, 14 Dec 2005, Kenneth Porter wrote:

> --On Thursday, December 15, 2005 8:15 AM +0100 Steffen Kaiser 
> <skmimedefang at smail.inf.fh-bonn-rhein-sieg.de> wrote:
>
>> OK, how to keep the "Bad Guys" out?
>> 
>> You're required to build up a trust system, then.
>
> Right, but we already do that with black lists.

Which had listed a major German freemail hoster some months ago 
regularily, so that I had to whitelist their IPs.

In opposite of blacklisting, where the sender can act upon a failure and, 
the probably queued, mails arrive the recipient eventually; you want to 
prevent that the mail is delivered, e.g.:

0) Zombie network prepares to submit SPAM messages,
1) half of the network lists the other half into the whitelist DNSBL,
2) the other half pushes out the SPAM.

You cannot do nothing, because the SPAM is already delivered.
Unlike with blacklisting, where you can manage a _late_ delivery, you 
cannot "undeliver" a message.

Hence, you (or "one") have to trust the Whitelist DB more than you need to 
trust a Blacklist DB.

Bye,

-- 
Steffen Kaiser