EWS not work

[trbl · Accepted solution]

You can also use the host name configured in the printer:

https://hp233426.mydomain.com/

[DukeOfDots]

Heureka!

The issue with the hostname and domain gave me the right clue.

If you want to connect to EWS from outside the intranet, means the internet, usually via router, maybe using dyndns service, you have to add the hostname (e.g. myprinter) _and_ the right domain name (e.g. dyndns.org) to the network identification setup page in EWS. So, if you have set up port forwarding in your router, in my case a Fritz!Box, the possible URL would be https://myprinter.dyndns.org:12345/

That has been the solution for my problem, reachable from intranet, but not from internet. Now it's working fine again, M479fdw serviceable from anywhere.

I think the cause is a forced valid certificate for secure connection, because you've been warned when changing the hostname that a new certificate will be generated.