How to Fix Windows Mail App Not Syncing or Running Slow

What Causes This?

The Windows Mail app usually slows down or stops syncing because its local cache gets corrupted, account sync settings are wrong, or background app permissions are disabled. It can also happen after a Windows update, when your internet connection is unstable, or when the Mail app is stuck with an outdated account token and can’t properly connect to your email provider.

Common Symptoms

• New emails do not appear unless you manually refresh
• The Mail app opens slowly or freezes when switching folders
• Sent, deleted, or read messages do not sync across devices
• You see sync errors, account errors, or repeated password prompts
• Mail notifications stop appearing even though messages arrive elsewhere

How to Fix It Manually

1. Check your internet connection and force a sync

   1. Open the Mail app.
   2. Select your account in the left pane.
   3. Click Sync in the top-right area of the app.
   4. If nothing updates, confirm your internet is working by opening a website in your browser.

2. Review your account sync settings

   1. In the Mail app, click the gear icon in the lower-left corner to open Settings.
   2. Select Manage Accounts and click your email account.
   3. Choose Change mailbox sync settings.
   4. Make sure email sync is enabled and that Download new email is not set too infrequently.
   5. Click Done, then Save.

3. Allow Mail to run in the background

   1. Press Windows + I to open Settings.
   2. Go to Apps > Installed apps.
   3. Find Mail and Calendar, click the three-dot menu, then choose Advanced options.
   4. Under Background apps permissions, set it to Always or Power optimized.
   5. Scroll down and make sure the app is not being restricted by battery-saving settings.

4. Repair or reset the Mail app

   1. Stay in Settings > Apps > Installed apps.
   2. Open Advanced options for Mail and Calendar.
   3. Click Repair first and wait for Windows to finish.
   4. Open Mail and test syncing again.
   5. If it still runs slow or misses messages, go back and click Reset.
   6. Note: resetting removes app data, so you may need to sign into your accounts again.

5. Remove and re-add the email account

   1. Open Mail > Settings > Manage Accounts.
   2. Select the affected account.
   3. Click Delete account from this device.
   4. Restart your PC.
   5. Open Mail again, choose Add account, and sign back in.
   6. This often fixes broken sync tokens and stuck account data.

6. Check for Windows and app updates

   1. Press Windows + I and go to Windows Update.
   2. Click Check for updates and install anything pending.
   3. Then open the Microsoft Store, click Library, and update Mail and Calendar if an update is available.
   4. Restart your PC after updates finish.

7. Close background apps if Mail is sluggish

   1. Open Task Manager with Ctrl + Shift + Esc.
   2. On the Processes tab, look for apps using high CPU, Memory, or Disk.
   3. Close apps you don’t need, especially browsers with many tabs or startup apps running in the background.
   4. Reopen Mail and check whether performance improves.

Fix It Automatically with Kudu

Kudu can automatically check for the common causes behind Mail sync problems and slowdowns, including app issues, background process overload, and Windows settings that interfere with performance. Instead of hunting through multiple menus, you can use Kudu to identify the problem quickly and apply the right fixes in one place.

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