本研究以商業日本語的課程實踐為基礎，提出學習者在商業mail中所使用的「待遇表現」並著眼於敬語表現，舉出實際的例子來分項做整理。整理時所採用的理論基礎為蒲谷宏・川口義一・坂本恵所提出的「丁寧的原理」，再交替宇都宮陽子「（さ）せていただく」與金東奎「オ願イシマス」的理論來做考察。探究學習者所犯的錯誤的原因，找出應該指導的學習項目與其內 容並且來建議。這也是本研究的目的。就結果來看學習者所犯的6種錯誤項目：1) 主旨的寫法、 2)收信人的寫法、3)對外部的人物的內部的人物的寫法、4)敬語表現的形與其使用方法、5)結語的打招呼的寫法、6)前置表現的誤用」等的事例來做為樣本提出，並透過其中誤用例來進行考察與檢討並探討其原因。最後來提出學習項目與其內容。

This study, based on actual teaching of Business Japanese, takes up attitudinal expressions used by students in their business mails, and, focusing on their use of honorific expressions, puts those examples in order as classified items. Theories employed in the classification are primarily based on the ＂Theory of Politeness＂ proposed b y Kabaya Hiroshi, Kawaguchi Yoshikazu, and Sakamoto Megumi , with also the theories expressed in Utsunomiya Yoko's ＂-sasete itadaku＂ and Kim Dongkyu's ＂Onegaishimasu＂ being considered as useful for our discussion. To decide and propose the exact learning items to be taught to students by probing into the causes of errors made by them is the object of this paper as indeed it is the role of us teachers as well. As a result, after studying and examining the errors as seen in those samples with their causes identified, we have been able to come up with and propose some exact teaching items classified into the following six areas: 1) Wording of the subjects of mails, 2) Wording of addressees' proper names, positions, and company names , 3) Proper distinguishing between out -group members as against in-group members, 4) Adequacy of honorifics in form and usage, 5) Wording of closing remarks, and 6) Incorrect use of introductory remarks.