As a legacy version, 5.6.3 has developed several significant maintenance challenges for those still running it:
This version is the ultimate release for macOS High Sierra 10.13.6 . macOS Server 5.6.3
(Mail, DNS, DHCP, VPN, Websites, Wiki, Calendar, Contacts) As a legacy version, 5
for new installs; fully functional for existing upgrades. Management Tools (Profile Manager, Open Directory, Xsan) Active and supported as the primary focus. As a legacy version
It served as a preparation point for the subsequent macOS Mojave-compatible version (5.7.1), which removed the vast majority of server features. The "Deprecated Services" Turning Point
The defining characteristic of version 5.6.3 is how it handles traditional server services. This version began the process of services from new installations to signal their upcoming removal. Feature Type Status in 5.6.3