Re: [Exim] Accepting relay ONLY IF from-address is valid ??

Hi Andrew, on Sun, 05 Oct 2003 02:50:26 +1000 you wrote:

> Is this possible?

Like most things with Exim, yes.

However, is it sensible?

Not unless you like being an open relay for spammers.

> I userstand that relay_from_hosts and
> relay_from_domains just allow mail to be sent from those
> domains/hosts...

Not quite. In the default config:

relay_from_hosts allows mail to be sent from the specified hosts

relay_to_domains (note *to* domains, not *from* domains) allows relaying
*to* addresses at the specified domain.

> I have users connecting from all sorts of places and need a
> way to get my server accepting any mail from anywhere for
> delivery

That's cool, but the way to do it is NOT to check the envelope sender -
that's an open invitation to spammers. The answer *IS* to use SMTP
authentication (SMTP AUTH). Read the manual/book. Search the mailing list
archives.

> IF the from-address is valid (which should be looked-up
> in a mysql table)

The problem with this is that any old spammer could use one of your
"valid" envelope senders and send unlimited mail through your machine!

Tim