Copilot in Outlook Signature Insertion: How It Handles Multiple Accounts

When you use Copilot in Outlook to compose an email, it can automatically insert your email signature at the bottom of the message. If you manage multiple email accounts in the same Outlook profile, you may notice that Copilot inserts the signature from your default account rather than the account you are sending from. This behavior can cause confusion and send the wrong contact information to recipients. This article explains why Copilot uses the default account signature, how to control which signature appears, and what to do when the signature does not match the sending account.

Why Copilot Uses the Default Account Signature

Copilot in Outlook generates email drafts based on the context of the conversation and the account you are actively using. However, when it inserts a signature, it reads the signature configuration from Outlook’s global settings. Outlook stores signatures per profile, not per message. The signature assigned to the default email account is the one that Outlook applies automatically to new messages. Copilot follows the same rule because it relies on the same underlying compose engine.

The default account is the first account listed in your Outlook profile. You can check this by going to File > Account Settings > Email. The account at the top of the list is the default. Even if you switch the “From” field in a new message to a different account, Outlook and Copilot still pull the signature from the default account. This is a deliberate design choice by Microsoft to maintain consistency across all compose actions.

If you have multiple signatures configured, each account can have a different signature assigned. But Copilot does not dynamically swap signatures based on the “From” address. It always uses the signature tied to the default account for new messages. For replies and forwards, Outlook uses the signature assigned to the account that received the original message, and Copilot respects that same behavior.

Steps to Configure Signatures for Multiple Accounts

To ensure Copilot inserts the correct signature for each account, you must assign a specific signature to each account in Outlook’s signature settings. Follow these steps.

1. Open Signature Settings
   In Outlook, go to File > Options > Mail. Click the Signatures button under the Compose messages section.
2. Create Signatures for Each Account
   In the Signatures and Stationery window, click New. Type a name for the signature, such as “Work” or “Personal.” Build your signature using the formatting tools. Repeat for each account you use.
3. Assign Signatures to Accounts
   In the Choose default signature section, use the E-mail account dropdown to select an account. Then select the signature you want for new messages and for replies/forwards. Repeat for each account listed in the dropdown.
4. Set the Default Account
   If you want a particular account to be the primary one, go to File > Account Settings > Email. Select the account and click Set as Default. This account’s signature will be used by Copilot for new messages unless you manually change it.
5. Test with Copilot
   Open a new message, switch the “From” field to a non-default account, and use Copilot to draft the email. Verify that the signature matches the sending account. If it does not, double-check the signature assignment in step 3.

If Copilot Still Inserts the Wrong Signature

Even after configuring signatures per account, you may encounter situations where Copilot inserts the wrong signature. This usually happens because of one of the following reasons.

Copilot Inserts the Default Signature Despite Correct Assignment

This occurs when the account you are sending from is not the default account. Copilot uses the default account signature for all new messages. To work around this, manually select the correct signature after Copilot generates the draft. In the message compose window, go to Signature > Signatures and pick the correct one. Copilot does not override a manually selected signature.

Signature Does Not Appear in Replies or Forwards

Outlook applies signatures to replies and forwards based on the account that received the original message. If you have multiple accounts, ensure each account has a signature assigned for replies/forwards in the Signatures and Stationery window. Copilot will then use that signature when generating a reply or forward.

Signature Is Empty or Missing After Copilot Drafts

If no signature is assigned to the default account, Copilot inserts a blank line or nothing at all. Go to File > Options > Mail > Signatures and assign a signature to the default account. Even if you rarely use that account, a placeholder signature prevents empty output.

Copilot Signature Insertion: Default Account vs Manual Override

Item	Default Account Signature	Manual Override
When it applies	All new messages composed with Copilot	After Copilot generates the draft, you select a different signature
Account dependency	Always uses the signature of the default account	You pick any signature regardless of the sending account
Persistence	Automatic for every new message	Lasts only for that single message
Configuration location	File > Options > Mail > Signatures > Choose default signature	Signature dropdown in the compose window
Best for	Users who send from one primary account	Users who regularly switch between multiple accounts

Copilot in Outlook inserts the signature from your default account when composing new messages. To make it use the correct signature for a different account, assign signatures per account in Outlook settings and manually override the signature after Copilot finishes drafting. For replies and forwards, ensure each account has a signature assigned for that action type. If you manage multiple accounts, consider setting the account you use most frequently as the default. You can also create a unified signature that includes all your contact details and assign it to every account to avoid confusion.