aside to the portable version of Thunderbird I use a normal installed one. All my data are stored on a different hard disc than the system and program files. In prior installations I moved the whole AppData directory to the other disc and created a link like
mklink /j AppData d:/AppData.
Since Windows 10 this is no longer recommended. Microsoft stated that Windows can't be updated when the AppData is moved and other users have had bad experience with this.
By changing the default location of the user profile directories or program data folders to a volume other than the system volume, you cannot service your Windows installation. Any updates, fixes, or service packs cannot be applied to the installation. We recommend that you do not change the location of the user profile directories or program data folders.
The only solution to this is to create symlinks for (nearly) all AppData directories – not nice but works :-(.
The only application that makes problems is Thunderbird Portable for it removes the symlinks
I've found some older posts about this. The problem was always blamed on a bug in the file system and the solution is to move the whole AppData to a different place. But Microsoft does not fix the filesystem since many years and I don't think they will ever do. And moving the AppData is no option anymore.
So I've got a big wish to the John T. Haller, the developer of Thunderbird Portable: Please build a workaround for the file system bug.
Or does anybody know a better way?