書信在日常生活及社會事務的處理中，占一定地位。書信作為外事交往的一種重要媒介，仍是我國同世界各國進行友好交往，開展對外貿易，交流情況，溝通思想，增進友誼的主要途徑。當然，這僅指一般事務性信件而言。至于書信作為一種社交手段，更是我們日常生活中相互聯系的必不可少的一部分。因此，了解書信的書寫要求，并認真地寫好，就顯得十分必要了。
 書信是書面的語言，它起着代言的作用。任何一封簡單的書信，都能反映出寫信人的思想認識、文化水平和處事态度，都會給人們一種深刻的印象和影響，尤其是涉外書信，由于其本身的特定作用，在外事活動、出國留學、文化交流和貿易往來中，政策問題、業務問題以及方法問題又處于十分重要的地位。因此，書信不僅能夠體現出我國的對外政策，也直接關系到我國的政治聲譽。所以，要正确有效地處理好這些問題，除了加強本身的學習外，還要有嚴肅認真的工作态度，這是寫好英文書信的基本要求之一。
 當然，寫好各種英文書信，并非輕而易舉。這不僅要求我們具備較堅實的語言基礎，還要求我們了解英文書信的書寫格式和行文要求，并在實際工作中，不斷地認真實踐。隻有這樣，我們才能寫好英文書信，發揮其應有的作用。
 現将英文書信的概況，以及書寫方法、行文風格等具體要求，分别介紹如下。
（一）英文書信的種類 (The Kinds of English Letters)
   英文書信大緻可分為事務信件（Business Letters）和私人信件(Private Letters)兩大類。
由于英文書信涉及面廣，用途極為廣泛，根據不同的作用和用途，還可細分為社交書信（Social Letters）, 私人信件(Private Letters) 以及一些既屬于事務書信又屬于私人書信的專門書信（Special Letters）和其他書信(Other Letters), 如表揚信（Letter of Commendation）、感謝信(Letter of Thanks) 等。
 值得指出的事，近年來在社會事務和對外貿易函件的處理中，非正式事務性函件(Informal Business Letters) 已被越來越多地使用。
（二）英文書信的格式 （The Forms of English Letters）
 英文書信，尤其是事務性信件，其書寫格式與漢語不盡相同，或者說完全不同。一般來說，英文書信的格式可以分為四種: 并列式/全封式(Blocked Form/ Full-block Format)、 斜列式/全縮式(Indented Form/ Fully Indented Style) 、折衷式/混合式/縮入式（Modified Form / Indented Style）和半封式（Semi-blocked Style/ Semi-block Format）
并列式/全封式 (Blocked Form/ Full-block Format)
并列式亦稱全封式，要求信頭、收信人地址、稱呼和正文（包括每段起行）均上下對齊。如果使用印有信頭的信箋，發信日期就要移至左邊，齊頭寫起。由于并列式左邊上下齊頭，便于打字，故常用于商業信件或正式信函。這些信函多半寫給不認識的人，如日常所說的詢問信、申請信和投訴信等。（見例1）
 例1：并列式/全封式 (Blocked Form/ Full-block Format)
 
 Madison and Moore, Inc.
 Professional Architects
 7900 South Manheim Road
 Crystal Springs, NE 71003-0092
 January 11, 2001
 Ms. Paula Jordan
 Systems Consultant
 Broadacres Development Corp.
 12 East River Street
 Detroit, MI 48001-0422
 Dear Ms. Jordan:
SUBJECT / Re: Request for alternate duplex plans, No. 32134 (This part can be omitted in informal letters.)
Thank you for your letter of December 3，2000. I have discussed your request with the
officials in our Planning Department and have learned that the forms we used are no longer available..
In searching through my files, however, I have come across the enclosed catalog from a Nevada firm that might be helpful to you. This firm, Nevada Designers, offers plans very similar to the ones you are interested in, as you can tell from the design I checked on page 23 of their catalog.
I hope this will help your project and I wish you success in your venture.
Sincerely yours,
Madison and Moore, Inc.
William Newhouse
Office Manager
Encl.: Catalog
注：(Encl.=Enclosure 附件)

 
例2：斜列式/全縮式 (Indented Form/ Fully Indented Style)
斜列式也稱全縮式或階梯式，要求信頭和收信人地址，均比上行縮進一點，呈倒梯形狀。正文每段起行，均向右縮進五個字母。

                                              
  246 Wall Street
                                                   New York 5, N.Y.
                                                        June 16th, 1982
 Mr. David Hall
    801 Oxford AV.
       San Francisco
 Dear David,
      I wonder if you have made any definite plan for the coming summer vacation.
 If not, I want you to come and stay with me for a few days. Every member of my
family will be very much pleased to receive you as a guest. You know that we do
not have a magnificent establishment and cannot afford luxuries but if you are
content to share a room with me and do not mind plain food you can be assured
of a hearty welcome and we shall do our very best to entertain you.
 Hoping you will be able to come, I am..
                           
                            Cordially yours,
                             D.  Johnson
  

例3：折衷式/混合式/縮入式（Modified Form / Indented Style）
   折衷式，也稱混合式，或縮入式。其信頭和收信人地址，上下各自對齊，正文每段起行，向右縮進五個字母。由于折衷式不拘于上述兩種格式，書寫方便，故目前使用較為普遍。

 
                                                   116 East 59th Street
                                                   Chicago 60637
                                                   U. S. A.
                                                   Mar. 14th, 1982
 Mr. Thomas Ray
 256 Cambridge Street
 London E. C. 2
 England
 Dear Thomas,
          My warmest congratulations to you on your receiving the regional scholarship to
 the State College of Engineering.
 It is an award that you richly deserve. I am sure that you will be a credit to
 the traditions of that fine school and to your chosen profession
 You have my very best wishes for your continued success.
 Sincerely,
                                  
                                   David Brown
    
                                               

 例4 半封式（Semi-blocked Style/ Semi-block Format）
      半封式與并列式/全封式基本相同，每個段落都不縮進，隻是将信頭及簽名縮至中線
 右側。如下所示。
 
                                             Department of Psychology
                                             The University of Reading
                                             Whiteknights
                                             P. O. Box 217, Reading
                                             United Kingdom
                                             RG 6 6AH
 December 22, 2000
  
    Prof. Li Yang
    School of Humanities
    Beijing University of Aeronautics
    & Astronautics
    Beijing, 100083
    PR China
  Dear Prof. Li,
    It is a pleasure for me to invite you on behalf of the Department of Psychology to
    accept an appointment as a visiting professor at the University of Reading from
    January 1, 2001 to June 30, 2001. The University of Reading will offer you an
    honorarium of ￡1250 per month and reimburse your travel expenses. We hope
    that you can accept this invitation and we ask you to contact Dr. Valerie Peterson
    with respect to details of your research and lecturing activities during your stay in
    Reading.
    I look forward to hearing from you.
   
    Yours sincerely,
 
                                                 Timothy Clarks
                                                 Chairman
                                                 Dept. of Psychology