[Marxism] tech note for verizon subscribers

Carlos A. Rivera cerejota at optonline.net
Wed Mar 2 12:02:57 MST 2005

Yes, but this is a non-RFC usage of 450 and other 4XX messages, it was 
pioneered by AOL, but its being copied by the big ones.

One of the reasons being that professional spamming software reads bounced 
messages and groups addresses according to bounce back message to prioritize 
address administration. By giving a 450, the hope is that the spam software 
would then demote address and not try it again for say, a week. After that 
period, they try again and again get the 450, and after a few tries, then 
delete the address altogether.

In theory, it is a good method. In practice, spammers are as keen on finding 
work-arounds as anti-spammers are, and the non-RFC uses of SMTP messages is 
actually creating a budding crisis in SMTP management; legitimate SMTP 
server for legitimate users might also evaluate bounce-back messages and 
take automated actions, such as not delivering email to a specific address 
even after the domain blocking happens.

It creates a vicious cycle of blocking and unblocking that reduces the 
effectiveness of email considerably.

Part of the fault lies in a market that demands server-side anti-spamming, 
but the bulk of the fault lies in major ISPs who don't like to do 
client-side anti-spamming.

In my professional opinion, server-side anti-spamming is useless as 
currently practiced.


----- Original Message ----- 
From: "Les Schaffer" <schaffer at optonline.net>

> RFC2821 says:
>   450 Requested mail action not taken: mailbox unavailable
>   (e.g., mailbox busy)

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