This expression is not only suitable for business mail, but also for greetings during telephone or line communication.
At other times, I can also say that I want to express the "hard work" of others. Of course, nowadays in Japan, the words "ぉにぉれさん" and "ごくろぅさん" are mostly simplified.
Many adults also greet their children after school with "ぉつかれさま". At this time, if they are their own parents, the children had better answer "ただぃま "; If it is an aunt or uncle, the children politely answer "こんばんはこんはちはさよぅな". "
In fact, the fuzziness of Japanese exists in all aspects, so friends must pay attention to choosing appropriate expressions according to different situations when using it ~ ~