User can't delete some mbox folders (after switching to Maildir)

[swelljoe]

See this thread for details: https://forum.virtualmin.com/t/cant-remove-mbox-format-folders-from-usermin/106898

[jcameron]

Looking at that ticket, it feel like maybe the folders are being deleted, but are then immediately re-created since they are defaults.

The real issue is that the existing drafts folder isn't recognized, because it's not in the expected dir. I'll fix this in the next release.