In Windows Live Mail under Drafts and also the subfolders under drafts . . . they are disappearing.

I have a new desktop Dell Windows 10 computer for about 5 weeks. The "Drafts" and subfolders underneath have disappeared 3 times.

I have to import them back from the exterior hard drive from the old computer back up.

Of course, I have added new ones since, of which I have lost entirely.

Why is the saved emails stored in the drafts disappearing?