1. network interface - check
2. dns - not applicable
3. firewall - check
4. ping - check
5. navigating to the web site - fail

There are two causes here. Either server fucks it self over or the client fucks itself over. For server check logs, for client: check spelling, specify full protocol and try different browser to pinpoint the problem. It would be great to see the full ip address output from ‘ip -c a’ on both client and server.

my users are not allowed to be mononym

I found the manual Can you get on that web site using a laptop? Can you log in, click on Internet, and take a screenshot (from a laptop)? Make sure to remove your public ip address form the screenshot. In your case it means remove ip addresses that does not start with 192.168.xxx.xxx

Is this your modem? https://help.iinet.net.au/how-setup-tg-789-broadband-gateway-nbn-fttbn

Can you access http://10.1.1.1 and log in as described? If so can you take a screenshot over that web site after you log in so we can see what settings are available to tweak? There might be a chance your modem-router will do just fine.

written in rust

👀

What the hell is JMAP anyway? Never heard of Another new alternative to IMAP. Can be read here.

i disagree with the color of the text. too much contrast. may I suggest it being dark blue?