I found a big bug at message search,when you input "xxxxx@naver. com"  or "@naver. com" at Search For,seems all the emails match the result.

You can try at your side,all versions,new version(6180),old version,all has such issue. Even you input @never.com to seach,the same,but if you input @qq.com @hotmail.com @gmail.com to seach,it has the correct result.