Help
Reply tracking
What it does
Keeps both sides of the ledger: who owes you a reply, and who you owe one to. When something's been sitting too long it drafts the follow-up in your own writing style.
Try this
“Who hasn't got back to me?”
What it needs
Nothing. It works from your mailbox.
What it won't do
Follow-ups are drafted, never sent automatically. Nothing leaves your mailbox until you say so.