Outlook is a powerful email client, but sync problems can be frustrating. In this article, we cover the most common sync issues and how to fix them.

Common sync problems

Recognizing symptoms

• Emails don't appear in Outlook while they're in webmail
• Sent emails don't appear on other devices
• Folders aren't synchronizing
• Deleted emails keep coming back
• Outlook hangs at "Synchronizing..."
• Error message "Cannot connect to server"

Solution 1: Check account settings

Verify IMAP settings

1. Go to File > Account Settings > Account Settings
2. Select your account and click Change
3. Verify these settings:

Incoming server (IMAP):

Outgoing server (SMTP):

Check authentication

1. Click More Settings > Outgoing Server
2. Ensure "My outgoing server (SMTP) requires authentication is checked
3. Select "Use same settings as my incoming mail server

Solution 2: Clear Outlook cache

Outlook stores emails locally. A corrupted cache can cause sync issues.

Rebuild OST file

Note: This can take some time with large mailboxes.

1. Close Outlook completely
2. Press Windows + R and type: %localappdata%\Microsoft\Outlook
3. Find the .ost file with your email address in the name
4. Rename the file (e.g., to old_account.ost)
5. Start Outlook again
6. Outlook will rebuild the cache from the server

Start Outlook in safe mode

Test if add-ins are causing the problem:

1. Press Windows + R
2. Type: outlook.exe /safe
3. If sync works in safe mode, disable add-ins via File > Options > Add-ins

Solution 3: Sync folder structure

Check folder subscriptions

With IMAP, you must subscribe to folders to see them:

1. Right-click on your account name in Outlook
2. Choose "IMAP Folders
3. Click "Query
4. Select all folders you want to sync
5. Click "Subscribe

Configure Sent Items folder

Ensure sent emails are saved on the server:

1. Go to File > Account Settings > Account Settings
2. Select your account > Change > More Settings
3. Go to "Sent Items tab
4. Select "Save items in the following folder on the server
5. Choose your "Sent" folder

Solution 4: Adjust offline settings

Set sync interval

1. Go to Send/Receive tab
2. Click "Define Send/Receive Groups
3. Select "All Accounts
4. Set "Schedule an automatic send/receive every to 5-10 minutes
5. Ensure "Perform automatic send/receive when exiting is checked

Make available offline

For full sync:

1. Go to File > Account Settings > Account Settings
2. Select your account > Change
3. Under Offline Settings, set the slider to "All

Solution 5: Fix connection issues

Check firewall and antivirus

Some security software blocks Outlook:

1. Temporarily disable your antivirus
2. Test if sync works
3. If it works, add Outlook as an exception in your antivirus

Solution 6: Repair Outlook profile

If other solutions don't work, create a new profile:

Create new profile

1. Close Outlook
2. Go to Control Panel > Mail (Microsoft Outlook)
3. Click "Show Profiles
4. Click "Add
5. Name the profile
6. Configure your email account again

Solution 7: Repair Outlook

Run Office repair

1. Go to Windows Settings > Apps > Apps & features
2. Find Microsoft Office or Microsoft 365
3. Click "Modify
4. Choose "Online Repair (more thorough than "Quick Repair")
5. Follow the instructions

Prevention: Avoid future problems

Regular maintenance

• Compact folders periodically: Right-click on folder > "Compact Folder"
• Archive old emails locally
• Keep your inbox manageable (no more than 10,000 items per folder)

Keep Outlook up to date

1. Go to File > Office Account
2. Click "Update Options > "Update Now
3. Install available updates

Need help?

We're here for you! Running into issues or have questions? Our support team is happy to help you personally. Drop us a message through the ticket system - we usually respond within a few hours and love helping you find the best solution.