I'm trying to move the local mail storage to a different location. As a test I've moved just one of the ~/Library/Mail/V5/hex-digits folders to my desktop and created a symbolic link in its place. I intend to just move the whole V5 folder at some point. For my test, when I open the mail app, the index of messages for this mbox is still there, but the heading on the mail app says that the store is (Read Only) and when I select a message I'm just getting a Loading... indicator.
The permissions don't appear to be different. Not sure what the problem is. Also, is there a better way to go about this? Hard links?