[OT] Routing?

[James Knott]

Henry Spencer wrote:
> 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.

Some ISPs, I believe Primus is one, allow access from off their network,
using a secure connection.  However, that's a different port, so
hopefully, Rogers or other won't block it.  If all else fails, there's
always a VPN or ssh.  When I'm on a different ISP, I can fire up my VPN,
to my home network and connect to the Rogers SMTP server.  As far as
they can tell, the connection is coming from my home computer.  I've
added a host route, so that all connections to them is via the VPN and
not directly through the ISP I'm connected to.


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