Error 0x800CCC0F means Outlook lost its connection to the outgoing mail server mid-send. A handful of related errors (0x800CCC0E, 0x800CCC19, 0x8004210B) all point to the same family of problems: a network hiccup, a misconfigured outgoing server, or something on your PC blocking the connection. Here is how to work through them.

1. Check Your Internet Connection First

Open a browser and load any website. If pages load fine, your internet is not the issue. If nothing loads, restart your router and try again before continuing.

2. Verify Your SMTP Server Settings

In Outlook desktop, go to File > Account Settings > Account Settings, select your email account, and click Change. Then click More Settings > Outgoing Server and Advanced. Common correct settings:

  • Gmail: smtp.gmail.com, port 465 (SSL) or 587 (TLS/STARTTLS)
  • Outlook.com / Hotmail: smtp-mail.outlook.com, port 587, STARTTLS
  • Yahoo: smtp.mail.yahoo.com, port 465 (SSL)

Make sure My outgoing server (SMTP) requires authentication is checked, and that it uses the same settings as your incoming server.

3. Temporarily Disable Your Antivirus Email Scan

Many antivirus programs intercept outgoing email to scan it. This can break Outlook's connection. Look in your antivirus settings for an Email Protection or Mail Shield option and disable it temporarily. If email sends successfully after that, add Outlook as an exception rather than leaving protection off permanently.

4. Try Sending in Safe Mode

Close Outlook. Hold Ctrl and click the Outlook icon in the Start menu (or run outlook.exe /safe). If email sends in Safe Mode, a faulty add-in is the culprit. Go to File > Options > Add-ins, set the dropdown to COM Add-ins, click Go, and uncheck add-ins one at a time to find the offender.

5. Create a New Outlook Profile

A corrupted profile can cause persistent send errors. In Control Panel > Mail > Show Profiles, click Add to create a new profile, then add your email account to it. Set it as the default and restart Outlook.

If none of these steps resolve the issue, ask us with your exact error code and email provider for more targeted help.