Good time of day. In fact, if you need it, you can easily improve it. You just need to create thunderbird signature and that's it. I recently did this to improve the quality of emails I send to my clients. And in fact this really sets me apart from others because not everyone knows that making an email signature is very effective.
I would recommend you to find useful sources, I mean books or lectures. You can ask some successful businessmen about it. But for me, the best solution is to pass a business English course. I will be the most efficient way. You will spend less time, you will have all materials you need, and most important - you will have a mentor you will be able to ask questions.