Goofy Mail Sort Problem

I searched on sort and haven’t seen anything to match. I have one user who has thousands of notes in his mail database - back to 2001. When he deletes a mail his mailbox resorts itself to end with the old mails and puts the focus on the very first mail in 2001. Sometimes it takes some of the old mails and puts them at the bottom while leaving the rest at the top and the current in the middle. No Full text index. I’ve done fixup, compact, replace design (which happens to be inotes6.ntf) Any suggestions or a direction to some documentation I may have missed?Thank you.