Scalix can mail to a@somehost.com, but not to b@somehost.com

[cari]

scalix runs fine here, omldapsync world nice with 2 ldap on SLES 10.
it relays mail over a relay host (1und1.de), better: it should.

Scalix is in a LAN, so the users have extern Internet Address like bla@gmx.de and blupps@web.de
But "bla" can only send to bla@gmx.de, not to another gmx address.
the error in the log shows:

sendmail[9308]: kA31ZI17009308: from=bla@gmx.de, size=0, class=0, nrcpts=1, proto=ESMTP, daemon=Daemon0, relay=localhost.localdomain [127.0.0.1]
sendmail[9315]: NOQUEUE: SYSERR(root): can not chdir(/var/spool/clientmqueue/): Permission denied

permissions are exactly set like http://www.sendmail.org/security/secure-install.php told me.

The Error i get per Mail:

b@somehost.com
because: A mail transport failure occurred
Supplementary Information:
WARNING: RunAsUser for MSP ignored, check group ids (egid 8, want )

somebody can help me at this point?
greetings, cari

[deyjvu]

Are you saying that each user has two Internet addresses and that if someone from the outside world sends to a user at one address like the blupps@web.de this mail is received in Scalix but if mail is sent to bla@gmx.de this mail is not delivered? Is this the problem?

If so, have you configured in your network to receive for both gmx.de and web.de?