tail -f /var/log/dovecot-sieve.log
Aug 07 15:33:45 lda(kec): Fatal: setgid(2000(vmail) from mail_gid setting) failed with euid=60011(kec), gid=50500(em), egid=50500(em): Operation not permitted (This binary should probably be called with process group set to 2000(vmail) instead of 50500(em))
Aug 07 15:33:45 lda(grosse): Fatal: setgid(2000(vmail) from mail_gid setting) failed with euid=519(grosse), gid=50500(em), egid=50500(em): Operation not permitted (This binary should probably be called with process group set to 2000(vmail) instead of 50500(em))