[OT] Routing?

[Henry Spencer]

On Mon, 27 Jun 2005, phil wrote:
> I'm baffled at the idea that a particular port responds or not, 
> depending on the source address or network.  (I know some providers 
> shut down SMTP from outside their network, but in this case: providing 
> 3rd-party mail is part of their business, there's no error message, and 
> it's strangely selective.)

It's not a question of the target machine responding or not depending on
where the call is coming from.  In the timeout cases, the call is never
reaching the target machine at all.

Many ISPs -- evidently including your cable supplier -- want outgoing mail
to go via their servers, so they can exert some control over spam attempts
etc.  So the only port 25 you can reach from within their network is
theirs; they block attempts to call out to port 25 elsewhere.  So the DSL
company's port 25 is unreachable from within the cable network.

                                                          Henry Spencer
                                                       henry-lqW1N6Cllo0sV2N9l4h3zg at public.gmane.org


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