A topic is a noun. A purpose is a verb attached to a person and a date. Load one of the four limp purposes below, then rebuild it slot by slot until an outsider could tell whether you succeeded. The diagnostics on the right update on every keystroke, and the finished statement turns itself into your opening line.
Start from a vague purpose
One document, one ask. If you find yourself typing a second verb into the action slot, you have two purposes fighting — and two short messages will be answered faster than one long one.
Your purpose statement
0of 6 diagnostics passing
The payoff: your opening line
The purpose statement lives at the top of your draft and gets deleted before you send — but it writes the first thing the reader sees. Fill the slots and this builds itself.