unwise filtering policy from cox.net

Paul Jakma paul at clubi.ie
Wed Nov 21 21:06:55 UTC 2007

On Wed, 21 Nov 2007, Sean Donelan wrote:

> 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.

> 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.

Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
A plumber is needed, the network drain is clogged

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