Block public namespace mail when quota exceeded

[Chris]

Dear All,

is it possible to temporarily reject mails, when quota of public namespace
subfolder is exceeded? I'd check folder size with a cronjob.

Dovecot is using a system user, so I guess blocking post and insert in ACL
isn't a solution?

I don't want to set the folder to read-only, that users can still delete
mails.

Thank you in advance.

- Chris