Just because emails are a quick form of communication, it doesn't mean emails, especially business emails, should be written using informal, shortened forms of words.
2018年12月四級真題（第二套）聽力 Section C
Museums and other institutions of informal learning may be better suited to teach this skill than elementary and secondary schools.
出自-2015年12月閱讀原文
Make full use of informal learning resources.
出自-2015年12月閱讀原文
Informal learning environments tolerate failure better than schools.
出自-2015年12月閱讀原文
For that, we have a robust informal learning system that gives no grades, takes all comers, and is available even on holidays and weekends.
出自-2015年12月閱讀原文
It has a very informal atmosphere, quite unlike some grand houses you visit.
出自-2013年12月聽力原文
Its informal conversational style would make interaction comfortable, and yet the machine would remain slightly unpredictable and therefore interesting.
出自-2013年6月聽力原文
Designers have also created informal gathering places, and upgraded employees' access to heavily trafficked areas such as copy and coffee rooms.
2015年高考英語上海卷 選詞填空 原文
No matter how formal or informal the work environment, the way you present yourself has an impact.