I haven’t done this in a while, but just today I tried to make a contact’s emails a VIP and found it no longer works. I don’t know if this is new to iOS 26 or was killed in a previous iOS release. I have a VIP mailbox, and when tapping on that and tapping add to list, my contact’s list appears, but tapping a contact just makes the list disappear with nothing added to VIP. In a message from that sender, tapping on the “From” name does not show a VIP option in the subsequent menu list. Does this still work for anyone?