You are replying to an email in Outlook and Copilot suddenly stops generating text mid-sentence. The cursor blinks, the suggestion window disappears, and you are left with an incomplete draft. This interruption happens because Copilot hits a timeout, a content policy boundary, or a data retrieval limit while composing. This article explains the three root causes that stop Copilot mid-reply and gives you the exact steps to resume drafting without losing your work.
Key Takeaways: Why Copilot Stops Mid-Reply in Outlook
- Copilot pane > Settings > Data sources > Microsoft Graph: Controls which emails and calendar items Copilot can read; restricted access stops generation mid-draft.
- Ctrl+Shift+Enter: Keyboard shortcut to manually submit the current text and restart Copilot generation from where it stopped.
- Microsoft 365 admin center > Copilot > Content policies > Sensitivity labels: Blocks Copilot from generating replies when the original email contains a protected label.
Why Copilot Stops Generating Mid-Reply
Copilot in Outlook uses a large language model hosted in Microsoft 365. Each reply request is a single API call. If the model takes longer than the server timeout threshold, the connection drops and Copilot stops mid-sentence. The default timeout for Copilot in Outlook is 30 seconds for standard tenant configurations.
Three specific conditions cause the stop:
Timeout on Long Drafts
When you ask Copilot to write a long reply, the model may exceed 30 seconds. Outlook does not stream the output incrementally in all versions. Instead, it waits for the full response. If the model takes too long, the request is canceled and you see a partial draft.
Content Policy Block
Microsoft 365 applies sensitivity labels and data loss prevention rules during generation. If the original email contains a confidential label, Copilot may stop mid-draft to avoid generating text that could expose protected information. The generation stops at the exact point where the policy is triggered.
Data Retrieval Limit
Copilot reads the original email thread and any referenced attachments to build context. If the thread exceeds 100 messages or the attachments total more than 20 MB, Copilot may stop generating because it cannot retrieve all the required data within the allowed window.
Steps to Resume Copilot After It Stops Mid-Reply
Use these steps to restart Copilot generation from the point where it stopped. Do not close the reply window.
- Press Ctrl+Shift+Enter to submit the partial draft
This keyboard shortcut sends the text Copilot already wrote as the current reply. It clears the generation state and prevents Outlook from thinking Copilot is still running. - Delete the last incomplete sentence manually
Remove the unfinished sentence so Copilot does not try to continue from a broken context. Keep only the complete sentences. - Open the Copilot pane and click Resume or Draft again
In the Copilot pane on the right side of the Outlook window, click the Resume button. If Resume is not available, click Draft and type a new instruction such as “Continue the reply about the Q3 report.” - Shorten your instruction to reduce generation time
Instead of asking for a full reply, ask for two paragraphs at a time. Example: “Write the first two paragraphs of a reply confirming the deadline.” - Check the sensitivity label on the original email
Open the original email and look for a sensitivity label in the header bar. If the label says Confidential or Highly Confidential, Copilot may stop. Ask your IT admin to allow Copilot generation on that label.
If Copilot Still Has Issues After the Main Fix
Copilot Stops Again After Resume
If Copilot stops a second time after you resume, the timeout is likely too short for your tenant. Contact your Microsoft 365 admin and ask them to increase the Copilot API timeout in the Microsoft 365 admin center under Copilot > Settings > API timeout. The maximum allowed value is 60 seconds.
Copilot Returns Generic Output Instead of Thread-Specific Data
When Copilot stops mid-reply and you restart it, the model may lose the context of the email thread. To fix this, manually paste the last few sentences of the original email into the Copilot instruction box. Type “Use this context:” followed by the pasted text, then add your instruction.
Copilot Does Not Appear in Outlook at All
If Copilot is missing from the ribbon or the reply window, the add-in may be disabled. Go to Outlook > File > Options > Add-ins. Under Active Application Add-ins, confirm Copilot is listed. If it is under Inactive Application Add-ins, select it and click Enable.
Copilot in Outlook: Draft Stop vs Timeout vs Policy Block
| Item | Draft Stop | Timeout | Policy Block |
|---|---|---|---|
| Description | Copilot stops writing mid-sentence without an error message | Server closes the connection after 30 seconds | Copilot stops because a sensitivity label or DLP rule is triggered |
| Visual indicator | Cursor blinks, Copilot pane shows no activity | Copilot pane shows “Taking too long” or a red error banner | Copilot pane shows “This content cannot be generated due to policy” |
| Fix | Press Ctrl+Shift+Enter and resume drafting | Ask admin to increase API timeout to 60 seconds | Ask admin to allow Copilot on the specific sensitivity label |
When Copilot stops mid-reply in Outlook, the cause is almost always a timeout, a content policy block, or a data retrieval limit. You can resume drafting by pressing Ctrl+Shift+Enter to submit the partial draft and then restarting Copilot with a shorter instruction. For persistent timeouts, ask your Microsoft 365 admin to increase the Copilot API timeout to 60 seconds. For policy blocks, check the sensitivity label on the original email and request an exception. Always keep the original email thread open so Copilot can re-read the context when you resume.