Mailbox not clearing up

Mailbox not clearing up

Hello!

We do experience a problem as our info box got a bit full, so we cleaned it up and now it doesn't appear to have a proper size - it is still full, though it is not what is marked under according user mail settings. How to actually permanently delete deleted messages that shouldn't take mailbox space, All of the messages are actually gone from the mailbox but it seems that they are somehow hiddenly stored.

SCREENSHOT FROM ADMIN VIEW


FROM USER MAIL SETTINGS


FROM USER INBOX FOLDER