Re: [anti-spam-wg] Re: [anti-spam-wg@localhost] Verizon blocking all IP addresses delegated by RIPE?

anti-spam-wg-request@localhost wrote:

> Date: Mon, 05 Dec 2005 16:01:11 -0800
> From: "MadGar" madgar@localhost
> Verizon is blocking email from a local high school email.  The email
> ends in  Thus, all email from the schools is returned to
> sender.

It is very common for email providers to use local and/or distributed
blocking lists. These are usually more or less dynamic. The more broad and
sensitive the blocking lists are, the higher the risk of "false

Since email addresses are easy to falsify, blocking is often based on
source IP addresses.

The refusal (most?) often takes place at the SMTP level. The permanent
failure status code is usually accompanied by a verbal explanation, often
stating in some detail the reason for the blocking. If, for example, the
MTA names a distributed blocking list, you may want to familiarize
yourself with the policies of that specific list in order to attempt