Howto Manage Default Dovecot Folders Through UCR Variables
Step 1
Stop Dovcecot service
systemctl stop dovecot
Step 2
Remove unwanted folders for a single account
doveadm expunge -v -d -u jane.doe@example.org mailbox Send\ Objects ALL
Step 3
Set default folders for all users
ucr set mail/dovecot/mailboxes/auto/NAME=[no|create|subscribe]
I.e.:
ucr set mail/dovecot/mailboxes/auto/Trash=subscribe
This allows to configure the automatic creation and subscription of folders. If set to create, the folder NAME is created automatically. If set to subscribe, it is also automatically subscribed. With the setting no nothing happens.