Copilot email signature
Microsoft 365 Copilot drafts in Outlook, sends from Copilot Chat and, in preview, runs agents with mailboxes of their own. Signatoro gives each of them your real signature.
How Copilot sends email
"Draft with Copilot" writes in Outlook's own message window, in new Outlook, Outlook on the web, classic Outlook, Outlook for Mac and the Outlook phone app. You keep the draft, edit it and select "Send".
Copilot Chat drafts an email in the chat, and for Frontier program users, "Open" moves it to Outlook while "Send" sends it from the chat. The Workflows agent, in Frontier early access, has Outlook actions to send an email, save a draft and reply.
Agent 365 agents can go further. In tenants in Microsoft's Frontier preview program, an agent can get its own user account, and Microsoft says that account "can hold licenses and Microsoft 365 resources such as a mailbox."
Why Copilot email loses or doubles the signature
Outlook adds your signature in its own message window, so "Draft with Copilot" keeps it. Microsoft does not say whether an email sent from Copilot Chat carries your Outlook signature, and an agent sending from a mailbox of its own has no signature until someone sets one.
The opposite happens too. Users report that Copilot ends a draft with a sign-off such as "Thanks," and their name, so the name appears twice above the Outlook signature.
How Signatoro gives Copilot your signature
You keep one signature on Signatoro, and Outlook, Copilot Chat and the agents you build all use it.
- Agentic sending: for sends from Copilot Chat, click "Copy as text" on Signatoro and add "End every email you draft with these lines:" and the signature to your custom instructions. Check the first email before you select "Send".
- API fetch and sync: an agent or flow that sends through Microsoft Graph or Power Automate calls the Signatoro signature API before each send and appends the HTML or text it returns, always the current version.
- MCP: Copilot Studio connects an agent to an MCP server by its URL, with OAuth sign-in, and Signatoro's is https://signatoro.com/mcp. The agent can then fetch your saved signature with get_signature.
- Agent mailboxes: add the agent's mailbox to your Signatoro company as a member. It gets the company brand like every person does, and the agent fetches that signature through the API.
- "Draft with Copilot": install your Signatoro signature in Outlook for new messages and for replies, and tell Copilot in "Draft Instructions" to leave out a sign-off and your name.
- Company signatures: an owner sets the name, logo, layout and, on the Up to 15 plan or larger, one footnote line for everyone, and every API or MCP fetch carries them.
When an email from Copilot should say AI wrote it
An agent with its own mailbox writes as itself, and Copilot Chat sends under your name. Whether either email should say an AI wrote it generally depends on where you are and what the email does. The disclosure guide covers what the rules typically ask, and a footnote line on Signatoro can carry the wording on every email.
Copilot email signature questions
Does Copilot add my Outlook signature to the emails it drafts?
Yes, in Outlook. Copilot writes into Outlook's message window, and Outlook adds the signature you chose for new messages and for replies. If it is missing, select "Signature" on the "Message" tab.
Why does Copilot add my name twice?
Users report that Copilot ends drafts with a sign-off and their name, above an Outlook signature that already has it. In new Outlook, select the dropdown next to the Copilot icon, then "Settings" and "Draft Instructions", turn on "Use custom instructions when drafting email" and write "Do not add a sign-off or my name."
Does an email sent from Copilot Chat include my signature?
Microsoft does not say. Select "Open" to finish the email in Outlook with your signature, or add your text signature to Copilot's custom instructions and check the draft before you select "Send".
Can a Copilot agent have its own mailbox?
In Microsoft's Frontier preview, an Agent 365 agent can get a user account that holds a mailbox. Add that mailbox to your Signatoro company as a member, and its email can carry the company signature.
How do I keep my signature current in email Copilot agents send?
Have the agent fetch it from Signatoro at send time, through the API or the MCP server. Each fetch returns the version saved on Signatoro, so an edit there reaches the next email.
Sources
Checked against Microsoft documentation on October 7, 2026.
- Microsoft: Draft an email message with Copilot in Outlook
- Microsoft: Draft and send email using Microsoft 365 Copilot Chat
- Microsoft: Get started with Workflows in Microsoft 365 Copilot
- Microsoft Learn: Agent 365 identity
- Microsoft Learn: Connect your agent to an existing MCP server
- Microsoft: Ask Copilot to make email drafts sound like you
- Microsoft: Add and change an email signature in Outlook