yum update sogo\* sope\* ytnef\* --enablerepo=nethforge-testing
or for a first installation
yum install nethserver-sogo --enablerepo=nethforge-testing
yum update sogo\* sope\* ytnef\* --enablerepo=nethforge-testing
or for a first installation
yum install nethserver-sogo --enablerepo=nethforge-testing
I just updated to 5.5.1 without any issues.