Hi, sys: Centos 5.2 x86_64 Trying to switch from sendmail to postfix I did: # yum remove sendmail which resulted in erasing of: mdadm sendmail-doc sendmail sendmail-cf mutt fetchmail redhat-lsb I did then: yum -y install redhat-lsb.x86_64 postfix and got this error: Installing: postfix ######################### [1/2] postfix: fatal: file /etc/postfix/main.cf: parameter setgid_group: unknown group name: postdrop warning: group postdrop does not exist - using root warning: group postdrop does not exist - using root warning: group postdrop does not exist - using root warning: group postdrop does not exist - using root Installing: redhat-lsb ######################### [2/2] I checked and indeed there is no group postdrop on the system. On an El5 system I see the group. Thx Rainer