Fix Microsoft Outlook Error 0x800ccc0b

Microsoft Outlook error 0x800ccc0b typically appears when sending email and means the outgoing mail server (SMTP) rejected the connection or authentication. The fix usually involves correcting your SMTP server settings, enabling authentication, or switching your outgoing port to 587 with STARTTLS. Below is a step-by-step guide to resolve it, plus background on why it happens and how to prevent it.

What Causes Error 0x800ccc0b?

Outlook uses the SMTP protocol to send messages. Error 0x800ccc0b is a generic client-side failure that often indicates one of the following:

• Wrong SMTP server address or port – your email provider’s outgoing server name or port number is incorrect.
• Authentication is disabled – many providers require “My outgoing server (SMTP) requires authentication” to be checked.
• Security settings mismatch – the encryption method (SSL/TLS or STARTTLS) doesn’t match what the server expects.
• Firewall or antivirus interference – a local program is blocking Outlook’s connection to port 25, 465, or 587.
• Outdated Outlook profile – corrupted account settings or a stale mail profile can trigger the error.

The error often appears right after you click Send, and the message may sit in your Outbox until you fix the settings.

How to Fix Error 0x800ccc0b (Step-by-Step)

Try these fixes in order. Most users resolve the issue with the first one.

1. Verify your SMTP settings. Go to File > Account Settings > Account Settings, select your email account, and click Change. Under Outgoing mail server (SMTP), confirm the server name matches your provider’s documentation (e.g., smtp.gmail.com, smtp.office365.com, smtp.mail.yahoo.com).
2. Enable SMTP authentication. In the same window, click More Settings > Outgoing Server. Check “My outgoing server (SMTP) requires authentication” and select “Use same settings as my incoming mail server.”
3. Change the port and encryption. Click Advanced and set the outgoing port to 587 with encryption type STARTTLS (or “TLS”). If your provider specifically uses SSL, try port 465 with SSL. Avoid port 25 unless your provider explicitly requires it.
4. Test with a new Outlook profile. Close Outlook, open Control Panel > Mail > Show Profiles, and create a new profile. Add your email account and test sending. This clears any corrupted profile data.
5. Temporarily disable firewall/antivirus. Turn off your firewall or antivirus for a minute and try sending. If it works, add Outlook to the exceptions list. Re-enable protection immediately after testing.
6. Update Outlook and Windows. Install the latest Office updates and Windows updates. Outdated software can have bugs that cause connection errors.

Common SMTP Ports and Encryption Settings

Most email providers support one of two standard configurations for SMTP:

• Port 587 with STARTTLS – the modern standard, works with Gmail, Outlook.com, Yahoo, and most business hosts.
• Port 465 with SSL/TLS – used by some older providers or those that require implicit TLS.
• Port 25 – historically used for SMTP, but many ISPs block it to reduce spam. Use it only if your provider specifically instructs you to.

If you’re unsure, check your provider’s help page for “SMTP settings.” Do not guess – an incorrect port is a leading cause of error 0x800ccc0b.

What to Do If the Error Persists

If you’ve verified settings and still get the error, try these additional steps:

• Check your email password. If your password changed recently, Outlook may be using an old one. Update it in Account Settings.
• Use an app password. If you have two-factor authentication enabled, your regular password may not work for Outlook. Generate an app-specific password from your email provider’s security settings.
• Repair your Office installation. Go to Control Panel > Programs > Microsoft Office > Change > Quick Repair. This fixes corrupted Outlook files.
• Recreate the email account. Remove the account from Outlook and add it again. This is often the final fix for persistent 0x800ccc0b errors.

How to Prevent Error 0x800ccc0b in the Future

Once fixed, you can avoid recurrence with a few habits:

• Always use the SMTP settings provided by your email host – don’t rely on memory.
• Keep Outlook and your operating system updated.
• If you use a VPN, ensure it doesn’t block SMTP ports. Some VPNs restrict non-HTTP traffic.
• Periodically verify your account password and authentication method, especially after changing passwords.

If you switch internet providers, re-check whether they block port 25 or 465 – some do, which can cause the error to reappear.

Comparison: Error 0x800ccc0b vs. Other Outlook SMTP Errors

Outlook has several similar SMTP errors. Here’s how 0x800ccc0b differs:

• 0x800ccc0f – “Connection to server failed.” This usually means the server is unreachable (network issue, server down).
• 0x800ccc67 – “Server rejected sender address.” This indicates the “From” address is not allowed on that server.
• 0x800ccc79 – “Server rejected recipient.” The recipient’s email address is invalid or blocked.
• 0x800ccc0b – “The connection to the server was interrupted.” Often a settings or authentication problem, not a network outage.

If you see 0x800ccc0b, focus on SMTP configuration first; if you see 0x800ccc0f, check your internet connection and server status.

Frequently Asked Questions

Why does error 0x800ccc0b only happen when sending, not receiving?

Receiving uses a different protocol (POP3 or IMAP) and a different server. Error 0x800ccc0b is specific to SMTP, so your incoming mail works fine while outgoing fails. This is normal and points to SMTP settings or server issues.

Can I ignore this error and still send emails later?

No. The email will remain in your Outbox and won’t be delivered until the error is fixed. If you close Outlook without resolving it, you may lose the draft or it will fail again on the next send attempt.

Does this error mean my email account is hacked?

Not usually. It’s a technical connection error, not a security alert. However, if you also notice suspicious activity (e.g., sent emails you didn’t write), change your password immediately and check your account’s recent activity.

Will changing my SMTP port affect my email security?

Using port 587 with STARTTLS is secure and recommended. Port 465 with SSL is also secure. Avoid using port 25 without encryption, as it sends data in plain text and is often blocked. Always use an encrypted port.

What if my provider doesn’t require SMTP authentication?

Some corporate or local servers don’t require authentication. In that case, uncheck the “My outgoing server requires authentication” box. But if you’re using a public provider like Gmail or Outlook.com, authentication is mandatory – enabling it usually fixes the error.

Does this error occur on Outlook for Mac?

Yes, but the settings are in different menus. On Outlook for Mac, go to Preferences > Accounts > Advanced, and check the outgoing server settings. The same principles apply: correct server name, port, and authentication.

Related

• Fix USB Composite Device Can’t Work Properly
• Share Wordle Results on iPhone or iPad
• How to Fix 0x80070057 During Windows Update