You can sort outlook messages by clicking on the category in the top. If you click on the Subject category, it will sort by subject. If you click on Date, it will sort by date.
You can try running outlook /cleanviews from the run line (close outlook first) to see if this is a views issue. It will reset all views to default. Start there and if you are still having the problem, let us know. Here are some other switches to try.Good luck to you!