Copilot in Outlook Writes Too Formal Replies: Fix Tone Settings

When you use Copilot to draft a reply in Outlook, the generated text often sounds overly formal or stiff. This happens because the default tone setting is set to Professional, which prioritizes polite and structured language over casual or conversational flow. Many business users find that replies sound like they were written by a corporate template rather than a real person. This article explains how to adjust the tone slider in Copilot for Outlook to match your preferred communication style, whether you want a short, direct message or a friendly, informal note.

Why Copilot Defaults to a Formal Tone in Outlook Replies

Copilot in Outlook uses a language model trained on a broad set of business communications. The default tone setting, labeled Professional, instructs the model to produce grammatically correct, polite, and structured responses. This is useful for executive emails or customer-facing replies, but it can feel unnatural for internal team chats or quick acknowledgments.

The tone slider is a simple one-dimensional control that ranges from Professional to Casual. Moving the slider changes the prompt that Copilot sends to the underlying language model. A more casual prompt uses shorter sentences, contractions, and less formal vocabulary. The slider does not change the factual accuracy of the reply, only the style of the language.

The feature is available in the new Outlook for Windows, Outlook on the web, and the Outlook mobile app. It requires an active Microsoft 365 Copilot subscription. Users with Copilot Pro may see a more limited version of the tone control.

Steps to Adjust the Tone Slider in Copilot for Outlook

Follow these steps to change the tone of a Copilot-generated reply before or after it is inserted into the email body.

1. Open the email you want to reply to
   In Outlook, click the email thread in your inbox. The reply area opens at the bottom of the reading pane or in a new window depending on your Outlook configuration.
2. Click the Copilot icon in the reply toolbar
   Look for the purple Copilot icon in the toolbar above the reply box. It looks like a small diamond with curved edges. Click it to open the Copilot reply pane.
3. Select a tone using the slider
   In the Copilot pane, locate the Tone slider. It shows Professional on the left and Casual on the right. Drag the slider toward Casual to reduce formality. You can also type a custom instruction in the text box above the slider, such as “Write this as a short, friendly note.”
4. Generate the draft
   Click the Generate button. Copilot creates a draft reply using the tone you selected. Review the text in the preview area before inserting it.
5. Insert the reply into the email body
   Click the Insert button to place the draft into the reply box. You can edit the text further before sending.

Adjust the Tone After Inserting the Draft

If you already inserted a draft and want to change the tone, use the Rewrite with Copilot option.

1. Select the inserted text
   Highlight the Copilot-generated reply in the email body.
2. Click the Copilot icon that appears above the selection
   A small Copilot toolbar appears with options including Rewrite, Summarize, and Adjust Tone.
3. Choose Adjust Tone
   Click Adjust Tone and then select Casual or another preset. Copilot rewrites the selected text with the new tone and replaces the original.

If Copilot Still Writes Too Formally After Adjusting the Slider

Copilot Ignores the Casual Tone Setting

If the slider is set to Casual but the output still sounds formal, the issue may be that the original email is very formal. Copilot tries to match the tone of the conversation. A highly formal original email can override the slider setting. To work around this, type a custom instruction in the Copilot pane, such as “Respond in a very casual, short tone as if talking to a colleague.”

Copilot Tone Slider Is Missing or Grayed Out

The tone slider may be unavailable if you are using an older version of Outlook or if your IT administrator has disabled the feature. Check that you are running the latest version of Outlook. In the new Outlook for Windows, go to File > Office Account > Update Options > Update Now. If the slider remains grayed out, contact your Microsoft 365 administrator to verify that Copilot features are enabled for your account.

Copilot Generates Replies That Are Too Short or Too Long

The tone slider controls style, not length. If the reply is too short or too long, use the Length setting in the Copilot pane. Length options include Short, Medium, and Long. Combining a Casual tone with a Short length often produces a natural, informal reply.

Item	Professional Tone	Casual Tone
Sentence structure	Full sentences with formal transitions	Short sentences, occasional fragments
Vocabulary	Polite phrases like “I would appreciate”	Direct phrases like “Please” or “Thanks”
Contractions	Avoided or rare	Frequent use of “don’t”, “can’t”, “I’ll”
Greeting and closing	“Dear [Name]” and “Sincerely”	“Hi [Name]” and “Thanks” or “Best”
Best use case	External clients, executives, formal requests	Internal team messages, quick acknowledgments

The tone slider is a quick way to control the style of Copilot replies in Outlook. If the default Professional tone produces text that feels too formal for your audience, drag the slider toward Casual or type a custom instruction. For persistent issues, check your Outlook version and verify that Copilot features are enabled. Using the Rewrite with Copilot option after insertion gives you a second chance to adjust the tone without starting over. Test the Casual tone with a Short length setting to see which combination matches your natural writing style.