[Dovecot] deliver to root

Hi,

we use dovecot 1.1.11 on a RH Server with sendmail. Local delivery is done with deliver:

Mlocal, P=/usr/local/libexec/dovecot/deliver, F=lsDFMAw5:/|@qSPfhn9, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL, T=DNS/RFC822/X-Unix, A=deliver -d $u

This setup works without issues for us, but mail to root has a problem with deliver:

deliver(root): Mar 04 16:31:31 Error: userdb(root) returned 0 as uid deliver(root): Mar 04 16:31:31 Error: userdb(root) returned 0 as gid deliver(root): Mar 04 16:31:31 Error: User root is missing UID (set mail_uid)

Is it generally not possible to use deliver to deliver mail to root?

Thanks Philipp