Why for some people is New Outlook not syncing automatically?

Question

Why for some people is New Outlook not syncing automatically?

Jeff Lamb 56

With an M365 mailbox in Exchange Online, user has an M365 E3 license, "New Outlook" is not automatically syncing and showing new email until the app is either restarted, or the user manually goes to View -> Sync.

The device is a Microsoft Surface laptop running Windows 11 24H2, latest security roll-ups.

How can the user control auto-sync and enable it? If there's no way, then what configuration or policies should we look for that might affect Outlook's ability to sync?

Jeff Lamb 56 Reputation points

2026-01-30T00:31:42.3266667+00:00

We solved the problem, but don't know why it was a problem. By simply clicking "sync" on the View ribbon, sync started working. We don't understand why Outlook didn't start the sync on its own through restarts of the app or even a reboot of the computer. Classic Outlook would at-least attempt to go online/sync at start-up.
Kai-L 17,480 Reputation points Microsoft External Staff Moderator

2026-01-30T17:26:29.4+00:00

Dear @Jeff Lamb,
Thank you for sharing the update! I’m glad to hear the sync issue is resolved, although I understand your confusion about why it wasn’t starting automatically.

There could be a few reasons why Outlook didn’t trigger the sync on its own, such as sync settings, background processes, or recent updates. Since you've managed to trigger the sync manually, it’s possible that the sync service was simply delayed or paused for some reason.

If this issue continues, I recommend checking the sync settings, clearing the Outlook cache, or even resetting the profile as a last resort to ensure everything is functioning as it should.

If you encounter the problem again or have further questions, feel free to reach out. Not only will I be happy to assist, but the professional community here is always eager to help as well.

Thanks again for the update, and I hope everything continues to work smoothly! Have a wonderful day.

Answer accepted by question author

Kai-L 17,480 Microsoft External Staff Moderator

Dear @Jeff Lamb,

Thank you for reaching out to Microsoft Q&A forum.

I’m sorry to hear you're experiencing issues with automatic syncing in the New Outlook. As a forum moderator, I genuinely wish I could directly access your account or delve into the backend systems to diagnose and fix this for you. However, our role here is limited to providing general guidance and solutions that can be applied by users.

From your descriptions, the issue is likely related to either a stalled local sync state, a Windows background activity, or a recent authentication/notification service regression. Since New Outlook is a web‑powered application, it requires a continuous, active connection to Microsoft 365 services. When that connection stalls, the app may stop updating until it is manually refreshed or restarted.

Please try the following steps to see if they help restore consistent syncing:

1.Disable "Offline Email" Mode

The app may be trying to manage a local database that has become "stale."

In New Outlook, click the Gear icon (Settings) in the top right.
Navigate to General > Offline.
Ensure "Enable offline email, calendar, and people" is turned OFF.
This forces the app to maintain a live, constant connection to Exchange Online rather than relying on its local sync timer.

User's image

2.Check "Background Apps" & Battery Policies

Aggressive power management on Windows 11 24H2 can "suspend" the Outlook process when it's not the active window, effectively killing the auto-sync.

Go to Windows Settings > Apps > Installed Apps.
Find Outlook, click the three dots, and select Advanced options.
Under Background apps permissions, ensure it is set to "Always".
Under Terminate, click the button to kill the process once, then restart the app.

User's image

Additional considerations:

Check if a policy is forcing frequent "re-authentication" via Entra Admin Center. If the token expires but the app doesn't prompt for a password, it will simply stop syncing mail until restarted.
If the Surface is using LTE or a hotspot, Windows may have flagged the connection as "Metered," which disables auto-sync by default to save data.
If your organization deploys updates via shared folders, the Jan 2026 patches may have failed to install correctly. Verify the "OS Build" is 26100.7623 or higher.

If none of the above solutions work, let me know in the comments for further investigation. Please note that our initial response does not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution. Thank you for your patience and understanding. I'm looking forward to your reply.

If the answer is helpful, please click "Accept Answer" and kindly upvote it.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Chris Duong 10,705 Reputation points Microsoft External Staff Moderator

2026-01-29T20:16:46.93+00:00

Dear @Jeff Lamb,

It has been a while, and we are writing to check in on how things are going with this issue. If there’s anything else we can assist you with, or if you need further clarification, please don’t hesitate to let us know, we’re here to help.

We look forward to hearing from you. Wishing you a wonderful day ahead!

1 additional answer

Your answer

Jeff Lamb 56 Reputation points

2026-01-30T00:31:42.3266667+00:00

We solved the problem, but don't know why it was a problem. By simply clicking "sync" on the View ribbon, sync started working. We don't understand why Outlook didn't start the sync on its own through restarts of the app or even a reboot of the computer. Classic Outlook would at-least attempt to go online/sync at start-up.
Kai-L 17,480 Reputation points Microsoft External Staff Moderator

2026-01-30T17:26:29.4+00:00

Dear @Jeff Lamb,
Thank you for sharing the update! I’m glad to hear the sync issue is resolved, although I understand your confusion about why it wasn’t starting automatically.

There could be a few reasons why Outlook didn’t trigger the sync on its own, such as sync settings, background processes, or recent updates. Since you've managed to trigger the sync manually, it’s possible that the sync service was simply delayed or paused for some reason.

If this issue continues, I recommend checking the sync settings, clearing the Outlook cache, or even resetting the profile as a last resort to ensure everything is functioning as it should.

If you encounter the problem again or have further questions, feel free to reach out. Not only will I be happy to assist, but the professional community here is always eager to help as well.

Thanks again for the update, and I hope everything continues to work smoothly! Have a wonderful day.
Chris Duong 10,705 Reputation points Microsoft External Staff Moderator

2026-01-29T20:16:46.93+00:00

Dear @Jeff Lamb,

It has been a while, and we are writing to check in on how things are going with this issue. If there’s anything else we can assist you with, or if you need further clarification, please don’t hesitate to let us know, we’re here to help.

We look forward to hearing from you. Wishing you a wonderful day ahead!

Answer 1

The issue of New Outlook not syncing automatically for some users can be attributed to several factors. Here are some potential causes and configurations to consider:

Modern Authentication: Ensure that modern authentication is enabled for the tenant. If it is not enabled, this could prevent automatic synchronization.
Mailbox Size: If the affected Microsoft 365 groups have 100,000 items or more, this may also hinder synchronization.
Cached Mode: If users are operating in cached mode, there might be synchronization issues, especially if mailbox items are changed through Exchange Web Services (EWS) calls. In such cases, users may need to clear offline items or switch to online mode to resolve sync issues.
Group Policies: Check for any Group Policies that may affect the automatic setup and synchronization of Outlook accounts. You can manage these settings through Group Policy or Cloud Policy services.
Conditional Access Policies: Review any Conditional Access policies that might restrict access or synchronization based on device compliance or location.

If these configurations do not resolve the issue, it may be necessary to further investigate specific settings or policies that could be impacting the Outlook application on the user's device.