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danthom's avatar
danthom
Copper Contributor
Jan 19, 2026

Issue with Outlook (Microsoft 365)

Hello.   I've an issue with Outlook when it's synchronising with server (receiving with pop.proximus.be).   When I do Send/Receive, I show the mails but the synchronisation never finishes.  It's ...
outlook
Jovansavage's avatar
Jovansavage
Brass Contributor
Jan 20, 2026

Hello!

This is a frustrating issue where Outlook gets stuck during synchronization. Let me help you troubleshoot this step-by-step.

Immediate Solutions to Try

1. Test in Safe Mode First

This will help identify if an add-in is causing the problem:

  • Close Outlook completely
  • Press Windows + R, type: outlook.exe /safe and press Enter
  • Try Send/Receive in Safe Mode
  • If it works, an add-in is likely the culprit

2. Clear the Problematic Email

Since it's getting stuck on the last mail, that message might be corrupted:

Access webmail to delete it:

  • Log into your Proximus webmail at https://webmail.proximus.be
  • Check for any unusually large emails or emails with strange attachments
  • Delete suspicious messages or move them to a folder
  • Try synchronizing Outlook again

3. Reduce Download Size Limit

Large emails can cause POP3 to hang:

  • In Outlook, go to File → Account Settings → Account Settings
  • Select your Proximus account and click Change
  • Click More Settings → Advanced tab
  • Under "Delivery", reduce the size limit (try 5 MB initially)
  • Check the box "Leave a copy of messages on the server" temporarily
  • Click OK and test

4. Repair Your Outlook Data File

Run the Inbox Repair Tool (ScanPST):

  • Close Outlook
  • Navigate to: C:\Program Files\Microsoft Office\root\Office16\ (or Office15 for older versions)
  • Run SCANPST.EXE
  • Browse to your .pst file (usually in C:\Users\[YourName]\Documents\Outlook Files\ or AppData\Local\Microsoft\Outlook\)
  • Click Start and let it repair any errors found

5. Check Antivirus/Firewall

Security software can interfere with POP3 synchronization:

  • Temporarily disable email scanning in your antivirus
  • Add Outlook and POP3 (port 110 or 995) to your firewall exceptions
  • Test synchronization again

6. Verify POP3 Settings

Ensure your Proximus settings are correct:

Incoming (POP3):

  • Server: pop.proximus.be
  • Port: 110 (or 995 for SSL)
  • Encryption: SSL/TLS if using port 995

Outgoing (SMTP):

  • Server: smtp.proximus.be
  • Port: 587 (with STARTTLS) or 465 (SSL)

Go to File → Account Settings → Change → More Settings → Advanced to verify these.

7. Create a New Data File

Since recreating your profile didn't work, try creating a fresh .pst file:

  • Go to File → Account Settings → Data Files
  • Click Add to create a new Outlook Data File
  • Set it as default
  • Re-add your Proximus account to use this new file

8. Clear Outlook's Send/Receive Groups

  • Go to Send/Receive → Send/Receive Groups → Define Send/Receive Groups
  • Edit your group and temporarily uncheck "Include this group in Send/Receive"
  • Create a new simplified group with just your Proximus account
  • Test with the new group

If Nothing Works

Alternative Approaches:

Switch to IMAP instead of POP3: POP3 is older and can have sync issues. IMAP is more reliable:

  • Remove your current account
  • Re-add it using IMAP settings:
    • Incoming: imap.proximus.be (port 993, SSL)
    • Outgoing: smtp.proximus.be (port 587)

Use Outlook's built-in troubleshooter:

  • Go to File → Options → Advanced
  • Scroll down and ensure "Enable Troubleshooting Logging" is checked
  • Review logs at %temp% folder for ETL files

Check Windows Event Viewer:

  • Press Windows + X → Event Viewer
  • Look under "Windows Logs → Application" for Outlook errors around the time of the sync issue

Try these solutions in order and let me know what happens. The webmail deletion approach (solution #2) combined with Safe Mode testing (solution #1) usually resolves most POP3 synchronization hangs.

 

Thanks,

Jovan S.

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