Mac Mail File Organization?

The V-folders are the version of Mail's database structure. V7 is Catalina, V6 is Mojave, etc.

If you have a later version, there shouldn't be anything in the previous folders. But, it sounds like if you imported both the V6 and V4 folders, they probably had duplicate information. You should only need to import a single V-folder, the latest.

When you upgrade the OS, the old folder should be deleted, but I have seen it left around. But, in those cases, there wasn't anything in the folder, email-wise. Just config files.

Containers are the App's sandbox, i.e. a place where it can safely play without interference from other apps, and it cannot interfere with them.

The Container has pointers to other areas of the OS. There is very little in the Container that is only in that container. Anything that you see in the Container that is somewhere else is likely just a pointer to that original information.

The messages and organization is stored in ~/Library/Mail, not in the sandbox, so deleting the Container folder should not affect that.

And I missed the part before when you said you changed the “geeky” names of the folders. Did it ever occur to you that those “geeky” names might be important to how Mail references the account folders? Changing the names would break all of the indexing done in the Envelope Index database if you did that in the Mail folder.

Well, yes, it is a lot more than pointers. They are Hard Links which are just inode references in the file system that point to where the actual data is stored. You can have thousands of hard links to a file and not take up any other storage.

When you look at a hard link in the file system, it appears to be a file. Anything that can display the storage space will almost always count all instances of the hard link as being the full size of the single storage space.

Oh, got it. I thought you changed the names in the folders inside the Container.