There are writers who outline and writers who rely on minute-by-minute, impromptu inspiration.
Put me solidly in the outlining camp. I believe that any complex writing project (including a business email) can be improved by outlining beforehand.
When I say "outlining", I don't necessarily mean the formal structure that most of us learned in school, with letters, numbers, and Roman numerals in both upper- and lowercase.
But writing typically goes better when the writer has a plan. More details in the video that follows: