letters/e-mail 'rules'

[Yoshiko]

hi!
I was wondering, what are the rules for a formal letter in Japanese? What sentences can be used as an opening/ending? Same goes for an informal letter. Regarding the latter, is it common to use informal speech also in letters or e-mail among friends?

Tokoro de, what is the English equivalent of 'yoroshiku' at the end of a letter?

[hatch_jp]

Formal letters consist of opening greetings, seasonal greetings, main topic, ginal greeting, and closing word, and it should be writen in extremely polite sentence and strict rule depend on situation. Even native Japanese don't know the rule so that there are many books and sites for writing a formal letter.
http://www.google.co.jp/search?num=100& ... %96%B9&lr=

Colloquial expression is used for intimate friends in letters and e-mail. A lot of icons are used in e-mail on a cell phone.