[exim] Is there any way to silently reject some recipients?

Hello.

Suppose user1 sends e-mail to user2, user3, user4. I want the following
conditions to be true:


1. SMTP session looks like completely successful for sender - no errors are
generated.

2. user2 and user4 are *silently* dropped from recipients address list - as
if there were no RCPT TO commands for them.

So only user3 should actually receive this e-mail.

3. All SMTP headers are kept intact.


I know that the best way to accomplish this task is to create mail rules at
client side. But unfortunately I can't do this.

So is there any way to do this at Exim's side? Thanks in advance,

Vitas.