Outlook should be able to SORT by different fields eg. Categories.

[Carlos]

In task list when I add fields to the view, such as Categories, or Companies,
and I try to sort the list by them, it says "You cannot sort by this field".
Why is that?

 

[Sue Mosher [MVP-Outlook]]

Categories is a multi-valued field. Any single item can have multiple
categories, so a straight sort is potentially meaningless or at least
doesn't reflect the richness of the data. Instead, you group by Categories.

Companies works the same way.