Outlook Error 0x800CCC0E: How to Repair SMTP Connection Refused

When you try to send an email in Outlook, you may see error 0x800CCC0E along with the message “Connection to the server was refused.” This error means Outlook cannot establish a connection to your outgoing mail server, also known as the SMTP server. The problem is almost always caused by incorrect account settings, a firewall blocking the port, or an antivirus program interfering with the connection. This article explains the root causes of the 0x800CCC0E error and provides step-by-step instructions to repair the SMTP connection so you can send email again.

Why Outlook Shows Error 0x800CCC0E When Sending Email

Error 0x800CCC0E is a client-side connection failure. Outlook sends a request to the SMTP server but receives no response or an active refusal. The most common causes are:

Incorrect SMTP server name or port number. Every email provider publishes specific SMTP server addresses and port numbers. If you type the wrong server name like smtp.gmail.com instead of smtp.office365.com, Outlook cannot locate the server. Using the wrong port, such as port 25 instead of port 587, will also trigger the error because many ISPs block port 25 to prevent spam.

Missing or wrong authentication settings. Most SMTP servers require authentication with your full email address and password. If the account is set to “Anonymous” or “No authentication,” the server refuses the connection. Some providers also require the option “Use Same Settings as My Incoming Mail Server” to be selected.

Firewall or antivirus blocking the connection. Windows Defender Firewall or third-party antivirus software may block Outlook from reaching the SMTP port. This is especially common after a Windows update changes firewall rules or an antivirus update re-enables email scanning features.

SSL/TLS encryption mismatch. SMTP servers require a specific encryption method. If Outlook is set to use “No encryption” but the server requires TLS, the connection is refused. Similarly, selecting SSL when the server expects STARTTLS will cause the error.

Server-side temporary outage. In rare cases, the email provider’s SMTP server is down or overloaded. This is less common than configuration errors but can happen during maintenance windows or DDoS attacks.

Steps to Fix the SMTP Connection in Outlook

Follow these steps in order. Test sending an email after each step. If the error persists, move to the next step.

Step 1: Verify SMTP Server Name and Port

1. Open Account Settings in Outlook
   Click File > Info > Account Settings > Account Settings. Select your email account and click Change.
2. Open More Settings
   In the Change Account window, click More Settings at the bottom right.
3. Check the Outgoing Server tab
   Make sure “My outgoing server (SMTP) requires authentication” is checked. Select “Use same settings as my incoming mail server” unless your provider specifically requires a different username and password.
4. Check the Advanced tab
   Look at the Outgoing server (SMTP) section. The Server port number must match your provider’s requirements. Common values are 587 for TLS or STARTTLS, and 465 for SSL. The encryption method below the port must match: TLS for port 587, SSL for port 465. Click OK.
5. Finish and test
   Click Next, then Finish. Send a test email to yourself.

Step 2: Change SMTP Port to 587 with TLS

If you are unsure which port to use, set Outlook to use port 587 with TLS encryption. This is the most widely supported SMTP configuration for modern email services including Microsoft 365, Gmail, Yahoo, and iCloud.

1. Open More Settings again
   Go to File > Account Settings > Account Settings, select your account, click Change, then click More Settings.
2. Set port and encryption
   Click the Advanced tab. In the Outgoing server section, change the port number to 587. Under “Use the following type of encrypted connection,” select TLS. Click OK.
3. Apply the change
   Click Next, then Finish. Try sending a test email.

Step 3: Allow Outlook Through Windows Firewall

1. Open Windows Security
   Press the Windows key, type Windows Security, and press Enter.
2. Go to Firewall settings
   Click Firewall & network protection, then click Allow an app through firewall.
3. Find Outlook in the list
   Scroll down to Microsoft Outlook or Outlook. Make sure both Private and Public boxes are checked. If Outlook is not listed, click Change settings, then Allow another app. Browse to C:\Program Files\Microsoft Office\root\Office16\OUTLOOK.EXE and click Add.
4. Save and test
   Click OK. Send a test email.

Step 4: Temporarily Disable Antivirus Email Scanning

Antivirus programs like Norton, McAfee, or Bitdefender often include email scanning features that intercept SMTP traffic. Disable this feature temporarily to see if it resolves the error.

1. Open your antivirus program
   Find its icon in the system tray or search for it in the Start menu.
2. Find email protection settings
   Look for a section called Email Protection, Email Scanning, or Web Shield. Disable the feature or set it to off.
3. Test Outlook
   Send a test email. If it works, re-enable the feature and add an exception for Outlook or for the SMTP port 587 in the antivirus settings.

Step 5: Create a New Outlook Profile

If none of the above steps work, the Outlook profile may be corrupted. Creating a new profile resets all account settings.

1. Open Mail in Control Panel
   Press Windows key + R, type control, and press Enter. Change View by to Large icons. Click Mail (Microsoft Outlook).
2. Create a new profile
   Click Show Profiles, then click Add. Type a name like Profile2. Click OK and enter your email account details. Complete the setup.
3. Set the new profile as default
   Under “When starting Microsoft Outlook,” select Always use this profile and choose the new profile from the list. Click OK.
4. Restart Outlook and test
   Open Outlook. Send a test email.

If Outlook Still Shows Error 0x800CCC0E After the Main Fix

Outlook Connects on One Network but Not Another

This indicates your network firewall or ISP is blocking the SMTP port. Some public Wi-Fi networks, corporate VPNs, or ISP-level filters block port 587 or 465. Contact your network administrator or ISP and ask if outgoing SMTP connections on port 587 are allowed. Alternatively, switch to a different network and test again.

Outlook Works for Receiving Email but Not Sending

This confirms the incoming server (POP3 or IMAP) is reachable but the outgoing SMTP server is not. Double-check the SMTP server name in Account Settings. A common mistake is using the incoming server name for the outgoing server. For example, Microsoft 365 uses smtp.office365.com for outgoing, not outlook.office365.com.

Outlook Sends from One Account but Not Another

If you have multiple accounts in Outlook and only one fails, the problem is specific to that account’s settings. Delete the account and re-add it using the automatic setup option. Go to File > Account Settings > Account Settings, select the account, click Remove, then click New and enter your email address. Outlook will attempt to configure the correct SMTP settings automatically.

Common SMTP Settings for Popular Email Providers

Provider	SMTP Server	Port	Encryption
Microsoft 365	smtp.office365.com	587	TLS
Gmail	smtp.gmail.com	587	TLS
Yahoo Mail	smtp.mail.yahoo.com	465	SSL
iCloud	smtp.mail.me.com	587	TLS
Outlook.com	smtp-mail.outlook.com	587	TLS

Use the table above to verify your account settings. If your provider is not listed, check their help page for the exact SMTP server name and port.

Conclusion

You can now fix Outlook error 0x800CCC0E by checking the SMTP server name, port, and encryption settings in File > Account Settings > More Settings. If the settings are correct, allow Outlook through Windows Defender Firewall and disable any antivirus email scanning feature. As a next step, create a new Outlook profile if the error persists after all configuration checks. For advanced users, use the telnet command in Command Prompt to test SMTP connectivity directly: type telnet smtp.office365.com 587 and verify you receive a 220 response from the server.