[EXIM] deliver without domain

Hi folks !

I've set up a little dialup-network with friends nd configured exim
to be the MTA.
It works fine till the point that
MAIL FROM: root
or
MAIL FROM: <MAILER-DAEMON>
shows up in my mailbox.
Of course exim refuses to accept these mails with a "sender must
contain a domain" (or similar).
But fetchmail then stops fetching my mail :-(

Is there a way to tell exim to accept those mails?

Thank you !

Regards,

Frank

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