Slow inbox

Hello,

I note the following problem. If the inbox holds many subfolders with mail, thunderbird spends a lot of time on startup.

To mitigate the problem, I asked users to keep the inbox clear of subfolders. However, a user keeps ignoring the local policy while also lamenting the mail is slow.

Please write instructions to enforce this local policy in dovecot, so that when users try to create an inbox subfolder, dovecot refuses the action.

Thank you