[Dovecot] localhost deliver(root at vlocalhost): setgid(5001) failed with euid=8, gid=8, egid=8: Operation not permitted

[Gert Cuykens]

How can i give lda dovecot permision to set user and goup id to 5001

dovecot      unix  -       n       n       -       -       pipe
 flags=DRhu user=mail:mail argv=/usr/lib/dovecot/deliver -f ${sender}
-d ${recipient}