[exim] Strange "Unrouteable address" issue

I noticed a pile of Queued email messages to root@??? in
the WHM email queue manager.

Roots mail on this server is being forwarded to a user@??? which is
on a different server.

This server is users9.xxx.xxx.domain.com and the other server is
company1.xxx.xxx.domain.com and hosts domain.com.

Force delivery of the messages result in:

Message xxxxxxx is no longer frozen
LOG: MAIN
cwd=/usr/local/cpanel/whostmgr/docroot 4 args: /usr/sbin/exim -v -M
xxxxxxx
delivering xxxxxxx
LOG: MAIN
** webmanager@??? <root@???> F=<>: Unrouteable
address
LOG: MAIN
Frozen (delivery error message)


Thanks, ideas would be nice. I have been looking at this so long that I
likely wouldn't see the problem is it stood up and poked me....