[Exim] Restricting local senders

Hi

I am attempting to stop a number of local users from sending emails (at
all) whilst allowing other users to continue as normal. I have been
looking at the acl configuration for this and think i need to use
something similar to:

acl_smtp_mail = acl_checknot_blockeded



begin acl

acl_check_notblocked:

  deny  senders  =
${lookup{$domain}lsearch{/etc/exim/blocked_email_addresses}{$value}fail}
        message = Email Access Is Presently Blocked

blocked_email_addresses    contains:

tcat.ac.uk        user1
tcat.ac.uk        user2

and so on

If anyone can suggest what is wrong with this approach or a better
approach i would be most greatfull

Thanks

Lee



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