Talk:MacOS Server/@comment-101.187.14.38-20151012110619/@comment-24886041-20151013035114

I can't recall if 10.9 was the first version where you could keep server.app; you  may have to pay for an El Capitan upgrade if you update. I do know that the Yosemite server.app works with El Capitan as well, but you'd do better to fully update. And the price is reasonable, especially compared to Office 365.