I deleted one email in Runbox 7, this vent to Trash.
Opened the iOS12 Apple Mail (IMAP) and the deleted mail is in Inbox, then opened the Trash in the same app, the deleted mail is downloaded to Trash, went back to Inbox, the deleted mail is still there. So now the same email is both in Inbox and Trash, in Rbox7 only in trash.
Way back in years when the DB2 was (and still is) the king a very useful motto was: Never touch a running system…
BTW: why on earth the title must be 15 characters long???