Rejecting clients that are not valid users only

[Troy McKinnon]

I am basically trying to configure my mail system so:

1) remote clients (cyrus mail users) can send from any location to any
location with no restrictions
2) incoming mail will be routed to local users (i.e. if it is final
destination)... from anywhere

I want my remote clients to be able to send whereever from whereever they
may be but I want to protect myself from ppl (Non users) just using my
server to send email.

While looking in my logs I noticed however that I was getting the following
error:

NOQUEUE: reject: RCPT from unknown[xxx.xxx.xxx.xxx]: 450 Client host
rejected: cannot find your hostname, [xxx.xxx.xxx.xxx];
from=<troy at mydomain.com> to=<troy at myotherdomain.com> proto=ESMTP
helo=<xxx.someotherdomain.com>

I found this possible solution:

http://mail-archives.engardelinux.org/engarde-users/2001/Aug/0132.html

i.e. the removal of:   smtpd_client_restrictions = reject_unknown_client

I am not sure if I like that solution.  Will that basically give me what I
am looking for? I don't want my users to not receive email from someone just
because their mail servers reverse lookup was not set up correctly. I want
to make sure they get all the email sent to them.  But I only want my cyrus
users to be able to send or relay email thru my system.

What setting should I set for this?


ALSO!! :) while I am on the subject...

Is there a way to have any rejected email for any of my virtual domains, to
any user be directed to my postmaster account... if it fails to find a valid
match elsewhere?