Outlook Emails Not Syncing Across Devices? Fix Missing Emails (2025)

Outlook Emails Not Syncing Across Devices? Here’s the Complete 2025 Fix

Are you seeing emails on one device but not on another? For example:

• Emails appear on Outlook Web but not on your laptop
• Emails show on your phone but not on desktop Outlook
• Sent emails missing on another device

This is a very common Outlook & Microsoft 365 sync issue in 2025, especially after updates, password changes, or account reconfiguration.

In this guide, you’ll learn why Outlook emails stop syncing and how to fix missing emails across devices step by step.

Common Symptoms of Outlook Sync Issues

• Inbox looks different on each device
• Emails missing on Outlook desktop
• Folders not updating
• Outlook says “Connected” but emails don’t update
• New emails appear only after restarting Outlook

Why Outlook Emails Are Not Syncing

The most common reasons include:

• Outlook is in Cached Exchange Mode with sync errors
• OST file corruption
• Account authentication or token issues
• Incorrect Send/Receive settings
• Outdated Outlook or Windows version
• Third-party antivirus or firewall interference

Fix 1 – Check Outlook Connection Status

1. Open Outlook
2. Hold Ctrl and right-click the Outlook icon in system tray
3. Click Connection Status

If you see repeated disconnects or authentication errors, Outlook is not syncing properly with Microsoft servers.

Fix 2 – Force Send/Receive Sync

1. In Outlook, go to Send/Receive tab
2. Click Send/Receive All Folders

If nothing changes or Outlook freezes, move to the next fix.

Fix 3 – Disable Cached Exchange Mode (Temporarily)

This helps identify OST-related sync issues.

1. Go to File → Account Settings → Account Settings
2. Select your email account → Change
3. Uncheck Use Cached Exchange Mode
4. Restart Outlook

If emails suddenly sync correctly, your OST file is likely damaged.

Fix 4 – Rebuild Outlook OST File

1. Close Outlook
2. Press Windows + R, type %localappdata%\Microsoft\Outlook
3. Locate your .ost file
4. Rename it (example: backup.ost)
5. Restart Outlook

Outlook will create a fresh OST file and resync emails from the server.

Fix 5 – Check Sync Issues Folder

Outlook quietly logs sync errors in hidden folders.

1. Press Ctrl + 6 in Outlook
2. Check folders named Sync Issues, Conflicts, or Local Failures

If errors are present, it confirms Outlook sync is failing internally.

Fix 6 – Update Outlook & Windows

Outdated builds often cause sync problems.

• Update Outlook via File → Office Account → Update Options
• Install pending Windows updates
• Restart your system

Fix 7 – Create a New Outlook Profile

If sync issues persist across all fixes, your Outlook profile may be corrupted.

1. Open Control Panel → Mail
2. Click Show Profiles
3. Add a new profile
4. Set it as default

This resolves most long-standing sync problems.

Why Outlook Sync Issues Should Not Be Ignored

• Important emails may never download
• Replies may go missing
• Calendar and contacts may stop syncing
• You could miss business-critical communication

Need Help Fixing Outlook Sync Issues?

If emails are still not syncing across your phone, laptop, and Outlook Web, the issue may require deeper diagnosis such as:

• Server-side mailbox issues
• Security policy conflicts
• Hidden authentication failures

In such cases, getting help from a Microsoft 365 expert can save hours of frustration and prevent data loss.

FAQ – Outlook Email Sync Problems (2025)

Why are emails missing only on one device?

This usually means the local Outlook data file is not syncing properly with the server.

Does rebuilding OST delete emails?

No. Emails are stored on Microsoft servers. Rebuilding OST only refreshes the local copy.

Can antivirus software block Outlook sync?

Yes. Some security tools interfere with Outlook traffic and cause sync failures.