Maybe everyone in your office grew up speaking Yiddish. Maybe you know for a fact that your client’s first language is the Nanchang dialect of Chinese. It seems easier and more comfortable to converse in the language your initial recipients, and/or you, are most comfortable with. But in many cases, it wastes a massive amount of time.
We work in connected world. Our employees, customers, clients, accountants, partners and lawyers may each be in a different area, and it's likely that not all of them are fluent in Yiddish or Nanchang.
As the message sender, the onus is on you to minimize the time your email takes to process. Even if it means taking more time on your end before clicking that send button.
The rule: It’s completely acceptable to choose whatever language you feel most comfortable with when meeting for coffee or chatting on a messaging app. But, the default language for emails is always English.
Key takeaway: Nobody likes to spend time translating an email before forwarding it to a non-Yiddish speaker in their organization. Stick to English.