Issue with Outlook (Microsoft 365)

Your Outlook POP3 account may be experiencing synchronization delays due to potential profile corruption or configuration issues. Microsoft advises verifying your account settings, reviewing mailbox size, and utilizing Outlook’s built‑in troubleshooting tools. If recreating the profile has not resolved the problem, consider repairing the Outlook installation, disabling non‑essential add‑ins, or migrating the account to IMAP for improved reliability and synchronization performance.

I can't send or receive messages in Outlook - Microsoft Support

Issues sending and receiving email - Microsoft Support

Classic Outlook profiles with POP accounts and PSTs hang after Windows updates on January 13, 2026 - Microsoft Support

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.