sogo doesn't have a stable repository for free, you need to go to the nightly repository. Here a way to build your own sogo rpm

First clone the sogo spec

git clone https://github.com/markVnl/SOGo-spec.git

Then inside adjust which version of the rpm you want, for that you can look in the nightly repo or in the web page. This is an example

Now go to build sogo build dependencies

dist=ns7 mockcfg=epel-7-x86_64 make-rpms libwbxml.spec
dist=ns7 mockcfg=epel-7-x86_64 make-rpms sope.spec

Once done we need to create a local repository because sogo needs some build dependencies you have just built

sope49-appserver-devel-4.9-20161202_324.ns7.x86_64
sope49-core-devel-4.9-20161202_324.ns7.x86_64
sope49-ldap-devel-4.9-20161202_324.ns7.x86_64
sope49-mime-devel-4.9-20161202_324.ns7.x86_64
sope49-xml-devel-4.9-20161202_324.ns7.x86_64
sope49-gdl1-devel-4.9-20161202_324.ns7.x86_64
sope49-sbjson-devel-2.3.1-20161202_324.ns7.x86_64
libwbxml-devel-0.11.2-3.ns7.x86_64

Therefore you must create a local repository where your files are. For example

sudo vim /etc/mock/nethserver-7-x86_64.cfg

modify accordingly where your files are and paste

[sogo]
name=sogo
baseurl=file:///home/lsd/dev/git_work/SOGo-spec

Obviously, this modification must be done on all mock architectures. For initiating your local repository (install first createrepo)

createrepo /home/lsd/dev/git_work/SOGo-spec

Now you can build by

dist=ns7 mockcfg=nethserver-7-x86_64 make-rpms sogo.spec

enjoy :)