The repository of Sme Server is not enabled by default, you need to past the command below in you terminal and launch the signal-event. If you want that a cron job will look after updates then you need to install smeserver-check4updates

db yum_repositories set stephdl repository \
BaseURL http://mirror.de-labrusse.fr/smeserver/\$releasever \
EnableGroups no GPGCheck yes \
Name "Mirror de Labrusse" \
GPGKey http://mirror.de-labrusse.fr/RPM-GPG-KEY \
Visible yes status disabled

After adding it to the database updating the configuration file is required:

signal-event yum-modify

Then for example

yum install smeserver-check4updates --enablerepo=stephdl

with smeserver you must launch an event after each installation, here it is

signal-event console-save

if you want to simply upgrade from my repository

yum update --enablerepo=stephdl