[Mimedefang] Re: Great open letter about anti-virus, emails, bounces, etc.

[Tony Langdon]

> Hrm ... I would expect that most ISPs would base your "relay-ability"
> on whether or not you were coming from their IP space.  If 
> you're coming
> from a single site (if I understand you correctly) then you're coming
> from IP space that they own, which should give you a blank check for
> relaying through the ISP's mail servers -- regardless of what domain
> you're claiming in your 'RCPT TO:'.  If Joe User claims to be somebody
> like billg at microsoft.com (a domain I happen to not host for 
> anyone :) ),
> as long has he's coming from my IP space, I don't care.  Anything else
> proved to be too much of a headache for us -- too many folks 
> need to do
> what you're describing.

The problem is if the ISP does that, then they're open to being victims of
relaying by spammers hacking their customers' machines, and we're back to
square one.  ISPs have had mixed policies here.  Some allow all relaying
from client IPs, others only allow a limited range of source domains.

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