[Exim] Blocking of unknown users...

Hello,

is there a possibility to block incoming mails by the recipient ???

This morning I was at a client which have his own mailserver and
they have gotten bounced messages, because of an illegal use of its
domain-name.

There are around 2500 bounced Messages for each of the around 400
random-arachters@???.

Now the link is an E1 with 256 kBit and the most E-Mails are large
because the stupid bouncing mailservers send the whole contents
with the error-message back !!!

And some mail-servers split the messages in multiple messages.

It is possibel for exim v4 to reject this mails immediately by
checking the headers ???

This will limit the traffic to some 100 Bytes and not 10 or more
kBytes each message.

The Client-Mailserver must accecpt only registerd users and
nothing else.

Thanks in advance
Michelle