[Sussex] spam filtering

[Steven Dobson]

Vic, Desmond

On Sat, 2006-08-19 at 12:47 +0100, Vic wrote:
> > Can we filter and in comparing the apparent sending address with the
> > actual is it possible to stop some of this problem?
> 
> Possibly.

But in reality not.

> If the domain owner has specified which IP addresses may send on behalf of
> his domain, then you can safely reject anyone else who claims to be
> sending from that domain.
> 
> This is called SPF.

But what about dial up and others on a randomly changing IP address?  If
your IP address isn't fixed then how are the domain owner's going to
allow the IP address I happen to be on at this moment as a ligitimate
sender or my email address?  Most well configured e-mail system will
reject e-mail connections that come from systems that are not known to
the Net databases are really e-mail server.

Now when I was on dial up all my outgoing e-mail when to my ISP's email
servers.  I bet a lot of people still configure their outbound e-mail
that way.  So is the owner of dobson.org going to configure my ISP's
e-mail servers as one allowed to send my e-mails?  This is only done at
domian level - so as any big e-mail portal like NetIdentity, GMail or
HotMail would have to allow _all_ ISPs to route their domains as they
are bound to have at least one customer with every ISP.

SPF's only work for some e-mail configurations, not all.

Steve
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