After reading several reviews, I chose ejabberd. Ejabberd can be downloaded from the previous link, but it also has the advantage of being located in the Ubuntu repositories. I created a Ubuntu Server and loaded ejabberd using “sudo apt-get install ejabberd”. Couldn’t be easier! And using a virtual machine to build the server means I can install it at customer locations without building a new server every single time, it will just need to be reconfigured once it is spun up.
Ejabberd is also part of the fedora repositories but not part of the CentOS repos.