guillemet [ˈɡiːmeɪ] :<< >>
bang:!
star:星星
yellow、orange、red、purple、blue、green
https://support.google.com/mail/answer/7190?hl=zh-Hant
搜尋標示為重要的郵件
is:important
label:important
範例:is:important
搜尋標示為yellow star
範例:has:yellow-star