unwise filtering policy from cox.net

Sean Donelan sean at donelan.com
Wed Nov 21 06:33:37 UTC 2007

On Tue, 20 Nov 2007, goemon at anime.net wrote:
> <abuse at cox.net>
>    (reason: 552 5.2.0 F77u1Y00B2ccxfT0000000 Message Refused.  A URL in 
> the content of your message was found on...uribl.com.  For resolution do 
> not contact Cox Communications, contact the block list administrators.)

An unfortunate limitation of the SMTP protocol is it initially only
looks at the right-hand side of an address when connecting to a
server to send e-mail, and not the left-hand side.  This means
abuse at example.com first passes through the same server as all of
the rest of *@example.com e-mail.  A single high-volume or special
address can easily overwhelm the normal email infrastructure (i.e. mailbox 
full) or the normal server administrators may make changes which affects 
all addresses passing through that server (i.e. block by IP address).

Even the FTC's UCE uce at ftc.gov e-mailbox has had problems, which 
affected the rest of *@ftc.gov e-mail.  So the FTC created a separate 
right-hand side name spam at uce.gov to separate UCE reports from normal
FTC e-mail channels which lets them route the mail with separate mail 
handling policies based on the right-hand side.

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