Free · works today
Use the built-in first
Turn on Dictation under System Settings > Keyboard. macOS may download a language file.
Open a message and click the body. Press the microphone key at F5 on MacBooks from 2021 on, or fn twice on other keyboards. A small A mic window appears. Speak the punctuation: "Thanks for the update period new paragraph" comes out formatted.
For more detail, see how to dictate on a Mac, and the Mac dictation commands cheat sheet.