NC E-mail App does not (always) reflect the details on the IMAP-server

Using Thunderbird, I moved some mailboxes as subboxes in the INBOX.
This is not reflected by the NC E-mail App.

I fail to understand why the NC E-mail App still has its own idea of how to represent the actual situation on the IMAP server, as that is the only truth that counts.
Refreshing does not solve this, neither does waiting.