I am using Microsoft Office 2007 in Windows XP. Many times, I get the SMTP error message in Outlook Express when I tried to send emails. "0x800CCC6B USER NOT LOCAL – User mailbox is known but mailbox not on this server" top on the screen. How can I fix this error message?
Hello,
SMTP error generally occur when outlook Express is experiencing problem regarding in authenticating Sender or the receivers' address. Here are some step in fixing or resolving the problem about the SMTP error. First, open the Outlook Express from the Start menu then, go to the TOOLS which is located at the MENU bar. From the down list, select the option ACCOUNTS.
The dialog box will open and show the internet Accounts, go to the MAIL tab and select your account ( just like in the given figure 1). Now after you select the email account, select the Properties and it will be open. Just select the tab called Server and place a Mark for “My server requires authentication ( as shown in figure 2) then click the OK and APPLY button. Then restart your outlook Express so that the above action will apply.
(figure 1) 
(Figure 2)
