Delete old object store mail

We had an object store in use a couple of months ago, since then it was detached, and with no way to reattach it, there are several mails sitting in the mailfiles that are inaccessible. We have copies of old mailfiles that are properly joined (from the old server) and I’d like to copy documents from those mailfiles to the current ones, however I dont’ want all those old invalid messages there as well. Any way to remove these? It doesn’t let you delete it for the same reason you can’t read it, because the object store doesn’t exist.

So basically, I just want to remove the headers from the mailfile for these broken links.

Thanks for any help!