What is the formal/polite way to begin and end an email in Chinese?
The traditional Chinese letter is very complex.It has many honorifics that vary greatly for different receivers.

But today,most people's traditional education is insufficient to write these letter.

For email,people tend to write simply and practicably。

Habitual formation。

                                                

example:

周老师：
    您好！
    我是Lorem ipsum dolor sit amet, consectetur adipisicing elit, 
sed do eiusmod tempor incididunt ut labore et dolore magna a...
    这个Lorem ipsum dolor sit amet, consectetur adipisicing elit, 
sed do eiusmod tempor incididunt ut labore et dolore magna a...
    敬祝！
安康！

                                                       学生 Jacob  敬上
                                                       2015.04.10


example 2:

陈英俊先生 道鉴
    去年入先生门下，承蒙恩师言传身教，宿愿得偿。中文潦草，敬启夫子。
     。。。。。。
     。。。。。。。。
     。。。。。。。。。。。

    敬请
 教安 
                                                        授业  张三顿首
                                                        乙未 二月廿二