[exim] Do not add qualify_domain to recipient 'root'

I have configured my Exim 3.35 so that every unqualified address gets the
domain name of our company appended to it, which is set with the keyword
qualify_domain.

But I do not want this behavior if the recipient is 'root'. Mails addressed
to 'root' shall only be delivered locally, never sent out to the smarthost.

How must I configure that?


Regards,

        Thorsten