So I tried installing Amazon Coretto instead of AdoptJDK and it's the same thing. davmail64.exe complains about not finding the appropriate JVM, despite the fact that it looks in HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\JRE, finds the subkey 11 there and I corrected the paths to point to Coretto (which evidently its installer did not do). Long story short, I can see in Process Monitor that it finds and even reads the value which contains the correct path to jvm.dll, but then I still get the dialog in which it complains about not finding a suitable 64-bit Java.