The filters don't work properly in the mail inventory (when trying to attach items to mail).
It's probably because the mail inventory doesn't have the "quest items" tab, which moves all of the icons apart from junk over to the right one space. It results in the filters being on the wrong tabs:
Apparel has filters for Drink, Food, Potion
Consumables has filters for materials/ingredients
Materials has filters for Containers, glyphs, etc |