If Outlook displays the error “Cannot synchronize subscribed folders,” it usually means Outlook cannot properly read the IMAP folder structure on the mail server.
By the end of this guide, you’ll confidently restore Outlook IMAP folder synchronization without contacting support.
Step-by-Step Fixes
There are a few different steps you can follow, and testing you can do to troubleshoot and fix this common Outlook error.
If you see this pop-up on your Outlook, it means that Outlook has not been set up to recognise that the server requires an Advanced IMAP configuration parameter to be put in place to properly read from the folder structure. This is called the IMAP Path Prefix.
1: Restart Outlook
Temporary synchronization errors sometimes occur due to cached processes.
Steps To Follow
- Close Outlook completely
- Wait a few minutes
- Reopen Outlook
IMPORTANT: Once you have completed the steps, check whether the folders synchronize.
2: Verify IMAP Root Folder Path
This fix only works if the server you’re connecting to uses IMAP as its mail server.
The most common fix is setting the Root Folder Path.
Steps To Follow
- Open Outlook
- Click File → Account Settings
- Select your email account
- Click Change
- Click More Settings
- Select the Advanced tab
- Locate Root folder path
- Using capital letters, enter “INBOX”
- Click OK, then restart Outlook.
3: Check Internet Connection
Synchronization requires a stable internet connection.
What To Verify
- You can open websites
- Webmail loads successfully
- Your network connection is stable
4: Update Outlook
Outdated Outlook versions can cause synchronization issues.
Steps To Follow
- Open Outlook
- Click File → Office Account
- Select Update Options → Update Now
IMPORTANT: Restart Outlook after updating.
5: Disable Antivirus or Firewall Temporarily
Security software can block synchronization requests.
How To Test
- temporarily disabling antivirus/firewall
- restarting Outlook
- testing synchronization
IMPORTANT: If testing resolves the issue, add Outlook as an exception.
6: Delete the Outlook Profile
Refreshing the account configuration can restore synchronization.
Steps To Follow
- Close Outlook
- Open Control Panel → Mail
- Click Email Accounts
- Remove the affected account
7: Create a New Outlook Profile
If the Outlook profile is corrupted, synchronization may fail.
Steps To Follow
- Open Control Panel → Mail
- Select Show Profiles
- Click Add
- Create a new Outlook profile
- Re-add the account in Outlook
Advanced (Optional) Fixes (For Technical Users)
Administrators, or Technical Users can diagnose deeper synchronization issues affecting Outlook clients.
1. Verify IMAP Server Connectivity
- Confirm that the mail server responds to IMAP connections.
- Test using:
telnet mail.domain.com 143 IMPORTANT: Successful responses indicate that the IMAP service is accessible.
2. Check Mail Server Logs
- Inspect server logs for synchronization or authentication issues.
- Common locations:
/var/log/maillog
/var/log/dovecot.log What To Look For
- IMAP authentication failures
- folder subscription errors
- connection timeouts
3. Inspect Mailbox Size and OST File Growth
- Large OST files may slow down or break synchronization.
- Check the OST size and compact the data file if necessary.
4. Review Firewall Rules
- Ensure the following ports are open:
IMAP: 143
IMAPS: 993 IMPORTANT: Blocked connections can interrupt synchronization.
Before You Move On
Checklist
- Root folder path is set to INBOX
- Outlook was restarted
- Internet connection is stable
- Outlook is updated
Next Recommended Steps
If Outlook continues to show folder issues, review:
If This Didn’t Work
Troubleshooting Completed But Issue Still Persists?
If the issue continues, contact support with:
- screenshot of the error
- Outlook version
- email address affected
Common Mistakes to Avoid
- Using lowercase inbox instead of INBOX
- Restarting Outlook without saving settings
- Assuming emails were deleted
Empowering Insight
Outlook synchronization issues usually stem from configuration mismatches, not data loss.
Correcting the root folder path typically restores folders instantly.
FAQs
Q. Will I lose my emails?
No, emails remain safely stored on the mail server.
Q. Will this affect my website?
No, this issue only affects email synchronization within Outlook.
Q. Why did my folders disappear?
Outlook may hide folders if the IMAP root path is incorrect.
Additional Resources
Recommended Server Settings for Email (Encryption & Ports)
How to Configure Email Clients
Viewing Your Email Settings in cPanel and Webmail
Viewing Your Email Settings in Windows Plesk
Access Email via Webmail
Need Additional Support?
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