Ok. My brief instruction for CentOS6.
Note, it is common instruction and you may have own nuances for your system.
1. Install all necessary packages:
# yum install rpm-build openssl-devel gcc make perl-Geo-IP perl-Mail-SPF perl-Net-CIDR-Lite
2. Download src.rpm package from Fedora repository:
# wget ftp://195.220.108.108/linux/fedora-secondary/development/rawhide/source/SRPMS/s/spamassassin-3.4.1-7.fc24.src.rpm
you can take this package from any other repository.
3. Build rpm package:
# rpmbuild --rebuild spamassassin-3.4.1-7.fc24.src.rpm
4. Update spamassassin:
# rpm -Uvh /root/rpmbuild/RPMS/i686/spamassassin-3.4.1-7.el6.i686.rpm
5. Check that it is up and running:
# /etc/init.d/spamassassin status
spamd (pid 21859) is running...