Office 365 Not Syncing with Outlook: Quick Fix Guide 2026

What Does “Outlook 365 Desktop App Not Syncing with Outlook” Mean?

When Office 365 is not syncing with Outlook, it means your mailbox is not updating properly across devices. You may see that new emails are not showing, sent messages remain in the Outbox, or calendar and contacts are not up to date. In some cases, the same account shows different data on desktop and web. This situation usually happens when the connection between Outlook and the server is interrupted or not working as expected, which prevents real-time updates.

Common Reasons Behind This Error:

• If your network is slow or disconnected, emails and updates will not load properly.
• If you enable “Work Offline,” Outlook stops syncing with the server.
• Wrong email settings or incomplete account setup can interrupt the connection between Outlook and Office 365.
• Using an old version of Outlook may cause compatibility issues with Office 365 services and stop proper synchronization.
• Also, when the mailbox becomes too large, syncing slows down or stops. 

How to Fix Office 365 Not Syncing with Outlook?

If your Office 365 emails are not syncing with Outlook, you can try some simple and effective methods to fix the issue. Follow each solution carefully to avoid mistakes and restore proper syncing.

Solution 01: Check Your Internet Connection

Outlook needs a stable internet connection to sync emails. Make sure your network is working properly. Open a few websites to confirm the speed and stability. If you are using a corporate network, make sure your firewall or proxy settings do not block Outlook connections (port 443 is commonly used).

Solution 02: Turn Off Offline Mode to Fix Office 365 Email Not Syncing with Outlook

• First, open Outlook and go to the Send/Receive tab.
• Then, look for the Work Offline option.
• If enabled, click it to turn it off.
• Once disabled, Outlook will reconnect and start syncing again.

Solution 03: Reconfigure Your Office 365 Account

• Go to File > Account Settings > Manage Profiles.
• Remove the existing account.
• Add your Office 365 account again.
• Enter the correct login details.
• Complete verification if multi-factor authentication is enabled.

Solution 04: Delete and Rebuild the OST File

• Close Outlook and press Win + R and type:
  • %localappdata%\Microsoft\Outlook\
• Find and delete the OST file.
• Restart Outlook.

Solution 05: Update Outlook and Windows to Resolve Office 365 Email Not Syncing with Outlook

To update Outlook:

• Go to File > Office Account.
• Click Update Options > Update Now.

To update Windows:

• Open Settings > Windows Update.
• Click Check for Updates.

Solution 06: Check Microsoft 365 Service Status

Sometimes the issue is not on your side. Microsoft services may be temporarily down. You can check the service status from the official portal. If there is an outage, you need to wait until Microsoft resolves it.

Simple Steps to Fix Office 365 Not Syncing with Outlook

1. Download and install the DRS Softech Office 365 Backup Tool.
2. Enter your Office 365 credentials, including ID & Password, to Sign In.
3. Preview and select the Office 365 emails to export. Click Next.
4. Choose Saving Format, like PST, from the drop-down list.
5. Lastly, apply basic and advanced features as per your needs. Click Convert.

Features of DRS Softech Office 365 Email Backup Tool

• Support bulk or large Office 365 emails with 100% accuracy.
• Offer Date Filter for selective email migration between a date range.
• Remove the Duplicate option to exclude duplicate files.
• Also, helps with migration from Office 365 Emails to Google Workspace.
• A free version of this tool is available to understand its features and functions.
• Additionally, it is highly compatible with all Windows and Mac versions.

Conclusion

Office 365 Not Syncing with Outlook is a common problem that many users face. But it can be resolved by using the right method. In most cases, the problem is caused by simple things like internet issues, incorrect settings, or corrupted files. These manual methods solved this problem in some cases. But the professional tool is the best solution to perform this process. It gives a guarantee that no data is lost. Furthermore, if you have any questions about this tool, feel free to contact our technical support.

Frequently Asked Questions