Here are the procedures to fix error 0x800CCC78 in Microsoft Outlook:

1. In your Microsoft Outlook 2007, go to Tools.
2. Go to Account Settings.
3. You should see the email account that you are using for this Outlook. Double click it.
4. Another new window will pop up – The internet E-mail Settings.
5. Click "More Settings”.
6. Click the Outgoing Server tab.
7. Put a check on "My outgoing server SMTP requires authentication".
8. Then press OK.