[Dovecot] RFE: Disallow DELETE of non-empty MBOX

[Kenneth Porter]

It looks like this is already the rule for maildir, where one can't remove 
the folder if any files or subdirectories are present. I'd like to get this 
option for mbox folders, as I'd like to prevent "accidents" where users 
accidentally delete large folders by clicking the wrong thing and then 
too-quickly approving the confirmation dialog that pops up. (Impatient 
upper level management tends to do this. ;))

BTW, I'm using Mulberry for my client, and it unfortunately puts "Mark 
contents seen" right next to "Delete folder" on the context menu. I'm aware 
of the issue so I tend to be extra careful when I finish with the folder 
associated with a busy mailing list and mark all the uninteresting messages 
seen.