777 of the most popular kanji from general Japanese might not be useful for work emails, but if you find the top 777 from a corpus of your own emails, it might

777 of the most popular kanji from general Japanese might not be useful for work emails, but if you find the top 777 from a corpus of your own emails, it might be. It's not hard - I've done this before using a corpus made up of work documents. There's a part-of-speech analysts tool called mecab that gives the word stems, and makes it easy to find word boundaries (since Japanese doesn't use spaces). The output went into Anki and it didn't take long before I was reading emails and documents at work fairly easily.