Someone forwards a paragraph into a thread and asks if you promised that date. The paragraph was in a message from your address. You used an assistant. You think you edited the date. You might have approved the draft as-is. The other person thinks a human typed it. You are now in a conversation about memory, not about the work.
You need who said what when the words will outlive the afternoon. Most AI-assisted mail has no way to answer that question. A From line names a mailbox. It does not name an author.
Three different claims hide in one message
The model wrote it. Useful, often right, not yours until you say so.
You approved it. You saw the draft and let it go. That is a signature on the assistant's wording, not a claim that you composed the sentences.
You wrote it. The note differs from the draft. The verbatim label exists for that case, and only on a path the server can see. Echoing the draft back is approval. A magic-link reply is typed by the recipient, never verbatim.
Your AI has opinions, not you. Mixing those claims in unlabelled prose is how a guess becomes "you said." The reader has no lever except to trust the whole block or none of it.
The fight is about a sentence, so the label has to sit on a sentence
A footer that says "drafted with assistance" is honest and useless at the point of quotation. The quoted line does not carry the footer. Provenance that lives next to the note, the assumption, the ask — that travels with the part being argued about.
Assumptions need it most. An unmarked premise reads as a fact you asserted. A labelled guess is a question the other person can cheaply correct. The cost of the unmarked one is not embarrassment. It is a plan built on a sentence nobody owned.
Approval is how ownership attaches
You confirm before send. That is the moment the From line and the words become a single act. Without it, "my assistant sent this" and "I sent this" are both true and both false, which is the worst possible record.
A later reader opens the package. They see the label. They see the note. They do not need you on the phone to interpret a chat you no longer have.
When you can skip the ceremony
"Lunch Thursday?" does not need a provenance stack. The words will not be quoted in a dispute. The moment a date, a number, a no, or a choice of vendor is in the sentence, you are in the other genre. Write it so a stranger can see who spoke.
If you cannot tell, yourself, which lines are yours, do not send yet. That confusion is what the other person will inherit, and they will inherit it as confidence.