Allowing Inbound Mail from specific hosts

We have our mail running through a third party spam filter. However
some spam still gets through because the spammer is ignorning our MX
records and guessing our e-mail server is the same IP as our webserver.
We can't easily change the SMTP server IP. All we need to go is make
our server deny any delivery of inbound e-mail that comes from a mail
relay that isn't one of the three servers the third party spam filter
service runs.

We are running Qmail on RH Linux with Plesk 7.5 Reloaded. What is the
easiest way to tell the server to reject all inbound mail delivery
accept from these three servers? Will still want clients to be able to
use our mail server as their outgoing SMTP server (we are allowing that
currently via authentication to prevent our server from being used as a
relay from an unauthorized client.)

Help!

In comp.os.linux.networking (E-Mail Removed):
> We have our mail running through a third party spam filter. However

My condolences.

> some spam still gets through because the spammer is ignorning our MX
> records and guessing our e-mail server is the same IP as our webserver.
> We can't easily change the SMTP server IP. All we need to go is make
> our server deny any delivery of inbound e-mail that comes from a mail
> relay that isn't one of the three servers the third party spam filter
> service runs.

> We are running Qmail on RH Linux with Plesk 7.5 Reloaded. What is the

Heard this "plesk" thing quite a few times, some admin tool/GUI
or alike? If you are serious about unix, I wouldn't use something
like this.

> easiest way to tell the server to reject all inbound mail delivery
> accept from these three servers? Will still want clients to be able to

Easy, just fire up a few rules 'iptables' ensure they are
reloaded on reboot and be done. Or check if qmail was compiled
with tcp_wrapper support and use that. Another option would be
any access control qmail offers like access.db sendmail uses.
I'd check the qmail documentation it should outline the needed
steps.

--
Michael Heiming (X-PGP-Sig > GPG-Key ID: EDD27B94)
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