Searching with two chars in English probably makes little sense. But in Chinese, two chars, or even one char, are discriminative enough. But KMail doesn't allow me to search with less than 3 Chinese chars: "The words less than 3 letters are ignored."
Raising severity, because the search is effectively not working for Han words.
Git commit 999bac0c064c600868af35852d2fe000aab09970 by Montel Laurent. Committed on 03/12/2017 at 07:52. Pushed by mlaurent into branch 'master'. Fix Bug 381777 - Please allow filtering with less than 3 (CJK) chars FIXED-IN: 5.8.0 M +6 -1 messagelist/src/core/widgets/quicksearchline.cpp https://commits.kde.org/messagelib/999bac0c064c600868af35852d2fe000aab09970