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Re: unwise filtering policy from cox.net

  • From: Paul Jakma
  • Date: Wed Nov 21 16:12:16 2007


On Wed, 21 Nov 2007, Sean Donelan wrote:



On Tue, 20 Nov 2007, goemon@xxxxxxxxx wrote:
<abuse@xxxxxxx>
(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.

full) or the normal server administrators may make changes which affects all addresses passing through that server (i.e. block by IP address).

I guess you're saying there's something architectural in email that makes it impossible/difficult (limitation) to apply different policy to the LHS.


That's not correct though. The receiving MTA is quite free to apply differing policies to different LHSes. And at least one MTA allows you special-case measures applied to tables of addresses, such as whether DNSbl lookups should be applied.

SMTP is distributed, so you do of course have to take care to keep distributed policy consistent. But, again, that has nowt to do with LHS/RHS of email addresses.

regards,
--
Paul Jakma	paul@xxxxxxxx	paul@xxxxxxxxx	Key ID: 64A2FF6A
Fortune:
A plumber is needed, the network drain is clogged