Here are the procedures to fix error 0x800CCC78 in Microsoft Outlook:
- In your Microsoft Outlook 2007, go to Tools.
- Go to Account Settings.
- You should see the email account that you are using for this Outlook. Double click it.
- Another new window will pop up. The internet E-mail Settings.
- Click "More Settings".
- Click the Outgoing Server tab.
- Put a check on "My outgoing server SMTP requires authentication".
- Then press OK.
