Comment 1 for bug 40413

Try View->SortBy->OrderRecieved (Or, if that's already how you view, try "Date")

Note that "sort by date" uses the "date" header, which could be wrong (intentionally or unintentionally) on some mails, so the "hidden" mails may just be WAY down in the list somewhere where you don't expect them.

Sort by "order recieved" uses the mailbox order, so may display them differently.