restricting mail user to internal mail

[Hans du Plooy <hansdp@newingtoncs.co.za>]

Hi all,

This is not my decision, but company policy of one of our clients:  I need to 
restrict some users to sending mail internally only, and also receiving no 
mail from outside.

So far I've done:
main.cf:

smtpd_recipient_restrictions =
                check_sender_access hash:/etc/postfix/restricted_senders
                check_recipient_access hash:/etc/postfix/restricted_recipients
                permit_mynetworks
                check_relay_domains
smtpd_restriction_classes = local_only
#local_only =
#       check_recipient_access hash:/etc/postfix/local_domains, reject
local_only =
        check_sender_access hash:/etc/postfix/local_domains, reject

And of course, made the appropriate restricted_senders ect files and hashed 
them.  As it is above, it works as far as blocking senders go.  If I 
uncomment the commented lines, it doesn't work at all.  I think the way I 
typed it is wrong (in form).  If I don't put the second "local_only=" in and 
just put the check_recipient_access and check_sender_access lines underneath 
each other, mail.log tells me that it's ignoring everything after the first 
"reject"

What is it supposed to look like?

Thanks
-- 
Kind regards
Hans du Plooy
hansdp at newingtoncs dot co dot za