Which version of 8.1 is it? I found that 8.1 2016-08-02 would not run on latest Windows 10, however I took the executable from 8.1 2016-08-30, pasted it into the client folder, and then it worked.
8.5 2023-04-19 (build 85550290)
In the server on the first run:
2025-10-29 09:07:29 Requesting Lookup address
2025-10-29 09:07:29 Failed to create e-mail back, unknown source register
What th...