It used to be possible in kmail1 to filter emails according to the categories of the contacts of addressbook. (there is a categories field in vCards) This isn't possible anymore with kmail2. For example : I set the categories tag "Friend" to my friends in the address book, and then I would like the kmail filter to move all emails coming from friends go to a specific folder. Reproducible: Always This is not yet possible in kmail 4.14.1
It's a good feature. I will try to implement it in kf5