@rfc2822 No, I can’t browse to the server from any device connected via Internet. On my local LAN the web pages serve up fine , and my Thunderbird calendar on a machine on the LAN will sync to the calendar on the Pi. However, I can ping the server successfully from the internet - both via direct IP address and the sub-domain name.
I do have a local DNS server running on another RPi on my LAN - Pi-Hole - to block ads. The Pi-hole logs don’t indicate that traffic to the sub-domain are blocked. But the DNS blocking would be happening from DNS resolution requests from devices that are connected on the LAN, not traffic coming into the LAN.