Managesieve problem

Hi,

I'ld try to set up the managesieve (for RoundCube) - the sieve is works as well with dovecot (I mean my filters works perfectly).

When I would try to connect to managesieve, I got an error, and mail.err contains:

dovecot: managesieve(airween@mydomain.hu): Error: user airween@madomain.hu: Couldn't drop privileges: getgrnam(vmail) failed: Permission denied (in mail_privileged_group setting)

Also I got it when I try to connect to port 4190 at localhost (with telnet), and send the generated AUTH string (with sieve-auth-command.pl).

Could anybody helps me to explain this message?

Thanks,

a.