Will Watermarking Stop Backscatter?

[David Jourard]

Ronny T. Lampert wrote:
>> Backscatter is becoming a real nuisance here. Can I stop it with
>> MailScanner? I did a "backscatter" search on the MS wiki but that
>> yielded nothing. How are all of you dealing with backscatter?
>
> How about taking the easier way and simply reconfigure your front-end
> and back-end servers to not accept any unknown recipients?
>
> For Postfix, simply add LDAP queries (I can help you with them, if you
> are e.g. using AD) - a matter of 5 minutes.
> For Sendmail I've been told it's also relatively easy ;)
I have one client  getting lots of NDRs. 

I want to stop all NDR email just for her email address.

Anyone know how to do this with sendmail or where I can find out.

Thanks in advance.
David J.