How do I get Notes to sync with macOS Server?

Hi,

I am facing challenges in getting Notes sync going between my iPhone 6 running iOS 10.2 and Mac running OS X El Capitan 10.11.6 and macOS Server 5.2.

Symptoms:

I am unable to see any reference to the OS X Server / macOS Server account or location inside Notes on the iPhone: unable to create a note in that location/account, unable to view folders/notes from that location/account, unable to sync (manually or automatically) notes from either my iPhone or iCloud to macOS Server.

On the other hand, on my Mac, I am able to see/add/select/edit notes under "OS X Server" location (which I have added through the Internet Accounts settings panel).

Potential Suspects:

- Mac built-in firewall interfering with iPhone access to Mac OS X Server?

- Mail option disabled when configuring OS X Server account in Mac and/or iPhone preventing Notes sync?

- other OS X Server service needing to be enabled?

- data pull/push model?

- others?

Setup:

- both Mac and iPhone are running on same private Wi-Fi network

- purchased, installed and updated OS X Server to latest version through Mac App Store on my Mac

- in the Mac Server app, left only Mail service enabled

- added OS X Server account on the Mac through Internet Accounts setting panel, with Notes option enabled (Mail option disabled)

- added MacOS Server account on the iPhone through Notes accounts settings panel, with Notes option enabled (Mail option disabled)

Background:

After years of mourning the loss of local sync through iTunes, I was very recently delighted to find out I could configure my iPhone to use a macOS Server account for PIM data sync in the respective settings panels (contacts, mail, calendars, reminders, notes). I took that as evidence I could once again implement local sync for Apple PIM data (including notes and reminders), through the use of OS X Server this time.