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

Common Synchronization Issues

Recognizing Symptoms

  • Emails do not appear in Outlook while they are in webmail
  • Sent emails do not appear on other devices
  • Folders are not synchronized
  • Deleted emails come back
  • Outlook hangs at "Synchronizing..."
  • Error message "Cannot connect to server"
  • Setting Up Cronjobs in DirectAdmin: Automate Tasks

Solution 1: Check Account Settings

Verify IMAP Settings

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

Incoming server (IMAP):

SettingValue
Servermail.yourdomain.nl
Port993
EncryptionSSL/TLS

Outgoing server (SMTP):

SettingValue
Servermail.yourdomain.nl
Port465
EncryptionSSL/TLS

Check Authentication

  1. Click on More Settings > Outgoing Server
  2. Ensure that "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 may take some time with large mailboxes.

  1. Completely close Outlook
  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. Restart Outlook
  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: Synchronize Folder Structure

Check Subscriptions to Folders

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

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

Configure Sent Items Folder

Ensure that sent emails are stored on the server:

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

Configure Trash/Deleted Items

  1. Same steps as above
  2. Go to the "Deleted Items tab
  3. Select the correct trash folder on the server

Solution 4: Adjust Offline Settings

Set Synchronization Interval

  1. Go to the 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 that "Perform an automatic send/receive when exiting is checked

Make Available Offline

For full synchronization:

  1. Go to File > Account Settings > Account Settings
  2. Select your account > Change
  3. Under Offline Settings, set the slider to "All
  4. Or choose a specific period (e.g., 1 year)

Solution 5: Troubleshoot 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

Check Proxy Settings

  1. Go to File > Account Settings > Account Settings
  2. Select your account > Change > More Settings
  3. Go to the "Connection tab
  4. Ensure that "Connect using HTTP is disabled (unless needed)

Solution 6: Repair Outlook Profile

If other solutions do not work, create a new profile:

Create New Profile

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

Delete Old Profile

Only after successfully testing the new profile:

  1. In Mail configuration, select the old profile
  2. Click on "Remove

Solution 7: Repair Outlook

Perform Office Repair

  1. Go to Windows Settings > Apps > Apps & features
  2. Search for Microsoft Office or Microsoft 365
  3. Click on "Change
  4. Select "Online Repair (more thorough than "Quick Repair")
  5. Follow the instructions

Issues with Specific Folders

Drafts Not Synchronizing

  1. Go to File > Options > Mail
  2. Scroll to "Save messages
  3. Ensure that "Automatically save drafts is checked
  4. Set the location to the server folder

Calendar Not Synchronizing

With IMAP accounts, the calendar does not synchronize automatically:

  • IMAP only supports email, not calendar
  • Use CalDAV for calendar synchronization
  • Or synchronize the calendar separately via another service

Prevention: Avoid Future Issues

Regular Maintenance

  • Compress folders periodically: Right-click on folder > "Compress 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 on "Update Options > "Update Now
  3. Install available updates

Need Help?

We are here for you! Are you facing any issues or have questions? Our support team is happy to assist you personally. Send us a message via the ticket system - we usually respond within a few hours and are happy to help you.