You see error 0x800CCC18 when Outlook cannot send or receive email. This error means your email server unexpectedly ended the secure connection. It is often caused by incorrect security settings or an outdated mail configuration. This article explains how to correct your account settings to resolve the error.
Key Takeaways: Fixing Error 0x800CCC18
- File > Account Settings > Change > More Settings > Advanced: Verify your incoming and outgoing server ports match your email provider’s requirements.
- File > Account Settings > Change > More Settings > Outgoing Server: Ensure the correct authentication method is selected for your outgoing mail server.
- Control Panel > Internet Options > Advanced > Security: Enable TLS 1.2 and TLS 1.3 to meet modern server security requirements.
Why Outlook Reports a Secure Connection Dropped
Error 0x800CCC18 occurs during the SMTP or IMAP handshake process. Outlook initiates a secure connection with your email server using protocols like SSL or TLS. The server then terminates this connection before the email transaction completes. This interruption is typically a configuration mismatch, not a permanent server fault.
The most common cause is using outdated security protocols. Many email services have disabled support for older protocols like SSL 3.0 and TLS 1.0. If Outlook is configured to use these, the server will drop the connection. Incorrect port numbers for the chosen encryption method will also trigger this error. Using port 465 for TLS instead of the standard 587 is a frequent mistake.
How Authentication Settings Cause the Error
Outgoing server authentication must match your provider’s setup. Some servers require the same settings as your incoming mail server. Others need a specific authentication type like NTLM or OAuth2. If this setting is wrong, the server accepts the connection initially but drops it when authentication fails.
Steps to Correct Your Email Account Settings
- Open Outlook Account Settings
Go to File > Account Settings > Account Settings. Select your email account from the list and click Change. - Review Server and Port Information
In the Change Account window, note your incoming and outgoing mail server addresses. Then click More Settings. - Configure the Outgoing Server Tab
Navigate to the Outgoing Server tab. Check the box for “My outgoing server requires authentication.” Select “Use same settings as my incoming mail server” unless your provider specifies otherwise. - Set the Correct Advanced Ports
Go to the Advanced tab. For incoming server IMAP, use port 993 with SSL. For POP3, use port 995 with SSL. For outgoing server SMTP, use port 587 with TLS or port 465 with SSL. Confirm these exact values with your email service. - Enable Modern Security Protocols
Close all dialog boxes and open the Windows Control Panel. Search for and open Internet Options. Go to the Advanced tab and scroll to the Security section. Ensure TLS 1.2 and TLS 1.3 are checked. Uncheck SSL 3.0 and TLS 1.0. Click Apply and OK. - Test the Account Configuration
Return to Outlook. On the Change Account screen, click Next. Outlook will test your account settings. If tests pass, click Close and then Finish. Send a test email to confirm the fix.
If Outlook Still Shows Error 0x800CCC18
Antivirus or Firewall is Blocking the Connection
Security software can interfere with Outlook’s secure connections. Temporarily disable your antivirus email scanning feature and any third-party firewall. Test sending an email. If it works, reconfigure your security software to allow Outlook or add it as an exception.
Outlook Profile is Corrupted
A damaged profile can cause persistent connection errors. Create a new Outlook profile via Control Panel > Mail > Show Profiles > Add. Set up your email account in the new profile with the correct settings. Set this new profile as the default and restart Outlook.
Email Provider Requires an App Password
Accounts with two-factor authentication often need an app password. Log into your email provider’s web portal and generate a new app password for Outlook. In Outlook Account Settings, replace your regular password with this app password in the account setup.
Manual Configuration vs. Auto-Discover: Error Impact
| Item | Manual Configuration | Auto-Discover Setup |
|---|---|---|
| Setup Method | User enters server names and ports manually | Outlook automatically detects settings |
| Error 0x800CCC18 Likelihood | Higher if ports or encryption are wrong | Lower, but can fail if auto-discover is blocked |
| Primary Fix Action | Verify and correct advanced port settings | Check network and registry for auto-discover issues |
| Best For | Older email services or custom domains | Major providers like Microsoft 365 or Gmail |
You can now send and receive email without the secure connection error. Ensure your port numbers and encryption types are always up to date with your email provider. For advanced control, use the Test Account Settings feature in Outlook to generate a detailed log. This log shows the exact point where the server drops the connection, helping you pinpoint the wrong setting.