Chapter in this post:
Today there is another tip that I have only just learned myself. These are folders or mailboxes in Apple Mail that cannot be deleted in the normal way. As a rule, this works by clicking on the folder in the Apple Mail sidebar with the right mouse button and then selecting "Delete mailbox". The mail program then throws out a warning message, which you confirm and then the corresponding folder should be gone.
In my case, it was folders from an IMAP mail account that I restored using Time Machine. I had deleted the mail account itself weeks before, so it was a local folder in Apple Mail. A few support documents indicate that you should contact your mail provider if you have problems with IMAP mailboxes, but - as already mentioned - these were local folders on my Mac.
You can see that I'm not the only person with the problem in question this and this Entry in the Apple support community. Among all the hints that you can find there, there was only one tip that really helped.
The solution to the problem works by deleting the mailbox files from the folder in which Apple Mail manages all of its data. The folder can be found on macOS Mojave under this path:
/ Library / Mail / V6
In older macOS systems the folder is V2, V3, V4 or V5.
By the way, you can get to the library folder by clicking on the "Go" menu in the Finder and then holding down the ALT key. The "Library" folder only appears in the list when the ALT key is pressed. In the library folder you will find a folder "Mail" and then the corresponding subfolder like "V6".
In this subfolder you then have to search through the subfolders until you find the mailbox files that are named like the mailboxes in Apple Mail that you want to delete.
Now you should close Apple Mail, delete the folder and then open Apple Mail again. In my case, the folders were still visible, but after I removed the folders using the normal delete function, they were actually gone.
If you like it short and sweet, you will find the short-and-painless version here:
In my case, the corresponding folders had disappeared after this procedure.
In any case, you should make a copy of the "Mail" folder before deleting the files. It contains all the important data so that you have a backup in an emergency.
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.