How to Fix Outlook Error 0x800CCC90 - Troubleshooting Guide

Microsoft Outlook users may encounter error code 0x800CCC90 when trying to send or receive emails. This SMTP (Simple Mail Transfer Protocol) error typically indicates a problem with your outgoing mail server connection. The error message often appears with additional information like "The connection to the server was interrupted" or "Outlook cannot connect to your outgoing (SMTP) email server."

Common Causes of Error 0x800CCC90

1. Incorrect SMTP server settings
2. Internet connection issues
3. Firewall or antivirus blocking Outlook
4. Outdated Outlook version
5. Corrupt Outlook profile
6. Email server problems
7. Incorrect authentication settings

Step-by-Step Solutions to Fix Error 0x800CCC90

Here are some methods to resolve the Outlook error 0x800CCC90 on your computer. You can also check another Outlook Error 0x80040116 which relates to mailbox sync issues and some solutions may coincide with the below solutions. 

Method 1: Verify Your SMTP Server Settings

1. Open Outlook and go to File > Account Settings

2. Select your email account and click Change

3. Verify the outgoing mail server (SMTP) settings:

   • SMTP server should match your provider's requirements

   • Port number is typically 587 (with TLS) or 465 (with SSL)

   • Authentication should be enabled

4. Click More Settings > Outgoing Server tab

5. Ensure "My outgoing server (SMTP) requires authentication" is checked

Method 2: Temporarily Disable Firewall and Antivirus

You can also do the following to fix Outlook error 0x800CCC90:

1. Open Windows Security settings

2. Temporarily disable firewall protection

3. Disable your antivirus software temporarily

4. Test sending an email in Outlook

5. Remember to re-enable protection afterward

Method 3: Repair Outlook Data Files

1. Close Outlook completely

2. Open the Control Panel and navigate to Mail (Microsoft Outlook)

3. Click Data Files and select your PST/OST file

4. Click Settings > Repair to run the Inbox Repair Tool (scanpst.exe)

For severely corrupted PST files that Outlook's built-in ScanPST.exe tool cannot fix, SysTools Outlook PST Repair provides an advanced solution. This specialized software efficiently recovers emails, attachments, contacts, and calendar items from damaged PST files, even when standard repair methods fail. Simply import the corrupted file, scan for recoverable data, and export the repaired PST for seamless restoration in Outlook. Ideal for large or heavily corrupted files, SysTools ensures maximum data recovery with minimal loss.

Working of the tool:

(Note: Always back up your PST file before attempting repairs.)

Method 4: Create a New Outlook Profile

Another way to fix Outlook error 0x800CCC90:

1. Open Control Panel and go to Mail (Microsoft Outlook)

2. Click Show Profiles

3. Click Add to create a new profile

4. Set up your email account with correct settings

5. Set the new profile as default and restart Outlook

Method 5: Update Microsoft Outlook

1. Open Outlook and go to File > Office Account

2. Click Update Options > Update Now

3. Allow Office to download and install updates

4. Restart Outlook after updates complete

Method 6: Check Internet Connection and Ports

1. Test your internet connection stability

2. Verify your router isn't blocking email ports (25, 465, 587)

3. Try connecting via a different network (mobile hotspot) to test

Advanced Troubleshooting Steps

If basic methods don't resolve the Outlook error 0x800CCC90:

1. Reset TCP/IP stack:

   • Open Command Prompt as Administrator

   • Type: netsh int ip reset and press Enter

   • Restart your computer

2. Reinstall Outlook:

   • Uninstall through Control Panel

   • Download fresh copy from Microsoft

   • Reinstall and reconfigure

3. Contact your email provider:

   • Verify server status and settings

   • Check if your account has sending restrictions

Preventing Future Occurrences

1. Regularly update Outlook and Windows
2. Maintain proper SMTP settings
3. Use reliable internet connections
4. Keep firewall/antivirus exceptions for Outlook
5. Periodically compact and repair corrupted PST file.

Conclusion: By following these troubleshooting steps, most users can resolve Outlook error 0x800CCC90 and restore normal email functionality. If the problem persists, consider contacting Microsoft Support or your IT department for further assistance.