[Mimedefang] Pre-Emptive Greylist entries

[Kenneth Porter]

On Tuesday, January 10, 2006 2:49 PM +1300 Roland Pope 
<rpope at jadeworld.com> wrote:

> Ie. When one of my users sends an  email from user at mynet.com to
> customer at custnet.com, I lookup custnet.com in DNS, get the IP's of the
> highest priority MX's and create a whitelist entry so that it decreases
> the chance that a reply from customer at custnet.com to user at mynet.com. gets
> delayed by the greylist code.

There's no guarantee that a domain's MX is the same addressed used for 
outbound mail. The larger the domain, the less likely that will be true, 
esp. if mail is outsourced to an ISP or a hosting provider.

Another approach is to use a wildcard greylist entry that ignores the IP 
address but causes the system to record the actual IP when a new message is 
seen.