A mail server that is operating as an open relay allows connections to
its SMTP port that permit the delivery to user on another domain.

If system A is an open relay, system B can connect to its SMTP port
and ask it to deliver mail to domains C, D, E, etc.

The majority of SMTP systems are (these days) configured so that they
will only deliver e-mail to people within their domain. Open relays
permit the delivery of all e-mail directed at them including that for
other domains. They are perfect (therefore) for those in the business
of generating SPAM since they allow the spammer to neatly cover their
tracks and have someone else's system deal with the load impoised by
their bulk mailings.

This is why open relays are considered BAD.

On 6/9/05, Mark Foster <blakjak@blakjak.net> wrote:
>
> Mikey wrote:
> > WOW, this sucks!
> >
> > Not only does Dan Langille insist on keeping all the email addresses in
> > the archives in a spam harvestable form, but he is also allowing his
> > server to operate an open relay, so anyone from any email address can
> > spam the list!
> >
>
>
> Wow, something sucks!
>
> Only I think you missed the point of what an 'Open Mail Relay' is.
>
> If you subscribe to this list you automatically agree to receive
> messages directed at the list address. Thus you can _unsubscribe_.
>
> Whilst I agree that subscriber-only might be wise in this day and age
> that in itself opens another can of worms.
>
> Implimenting sub-only means screwing around with people who subscribe
> using a different address to that which they post with, etc.
>
> So erm, yeah, you might like to perhaps direct any feedback you have
> about Dan and the way he runs this list, _to Dan_, instead of bothering
> the rest of us with it.
>
> Cheers
> Mark.
>
>

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