The problem
A lot of the day is writing the same kinds of email to different people: the update to a client, the reply to a supplier, the note to the site team. Each one has to sound right for who it is going to. Each one gets written from scratch, or copied from an old one and then reworked until the copying shows.
What it does
You name the recipient and say, in a line or two, what the email is for. The system uses the tone you have set for that recipient, whether formal, transactional or friendly. It drafts the email as you would write it: your phrasing, your sign-off, the things you always mention and the things you never do. You read it, change what you want, and send it.
What it needs from you
A stack of your own sent emails, enough to show how you write to different people. A note of who gets which tone, which is usually obvious once it is written down. Access to your mailbox, arranged so that you can withdraw it.
What it does not do
It does not send anything. It does not reply to emails on its own, and it does not read your inbox looking for things to answer. It does not know what was said on the phone yesterday unless you tell it. A person reads every draft before it goes. The first drafts will be slightly too polite or slightly too blunt for somebody. Your corrections are how the tone gets tuned.