[Exim] error: sender verify failed

Hi,

On a Exim 4.10 box, AFAIC, the same setup as on another box. When a
client from the local network tries to send email, this results in error
messages like:

  2002-11-29 19:51:46 H=xpert.local (xpert.zenger.nl) [10.0.1.1] sender
        verify fail for <peter@???>: Unrouteable address
  2002-11-29 19:51:46 H=xpert.local (xpert.zenger.nl) [10.0.1.1]
        F=<peter@???> rejected RCPT <peter@???>: Sender
        verify failed

What I do not understand is that it cannot verify <peter@???>?

I have tried to find the exact way of verifying in the docs, but that
did not really help. Is this an error because of a faulty DNS setting?
Or is this something else?

TIA.

--
Rejo Zenger <rejo@???>
http://www.xs4all.nl/~sister
PGP 0x75FC50F3