This behavior may occur if either of the following conditions is true:
• You import mail from Outlook into Outlook Express, but you removed Outlook from your computer before you tried to import the mail into Outlook Express.
• You configure Outlook Express to be the default Simple Messaging application programming interface (MAPI) client.
• You import or export mail from Outlook Express, and you do not have Outlook installed on your computer.
To resolve this issue, try one of the following methods, as appropriate for your situation.
Method 1: If you want to use a special program you can use Outlook Express Fix Toolbox
Method 2: Change your MAPI Settings
Configure Outlook Express to not be the default Simple MAPI client before you import the mail items. To do this, follow these steps:
1. Restart your computer, and then start Outlook Express.
2. On the Tools menu, click Options.
3. On the Connection tab, click Change to open the Internet Properties dialog box.
4. On the Programs tab, click an e-mail application other than Outlook Express in the E-mail list. Click Apply, and then click OK.
5. Click OK again to close the Options dialog box.