Re: Advanced tricks I use to get rid of spam using MX 4xx

[Marc Perkel <marc@perkel.com>]

Uncle George wrote:
> Yes, maybe MX15 will accept the message! Maybe MX20 will accept the 
> message. You wont know till you try.
> As the original poster stated, a long time ago, his service  
> greylist's everyone on the lowest MX. But apparently accepts, without 
> greylisting, on the next MX.  This on the presumption that spammers 
> will only try the lowest MX, and ignore the higher MX's. Real MTA's, 
> as per 2001 spec's, would have tried at least the 2 very lowest MX's, 
> if not the preconfigured limit, or all of the MX's .
> Its not for me to say what the reasons ( or reasonableness ) are for 
> why this SMTP strategy is acceptable for some. Or even why such 
> matters have to be codified in an RFC .
Except for the qmail problem, if someone wanted to get dir of say 90% of 
all their spam here's an easy way to do it.
You have 3 MX records. The highest and lowest both return 4xx on 
everything. The middle MX accepts all. Then you block with a few of the 
better black lists and you have a spam filter that is more accurate than 
using Spam Assassin by itself.
I use both. When I get down to the last 10% I can cull out half the good 
email with my whitelist tricks and that leaves only 5% for SA.