Here are a few possible solutions:
Reinstall MS Outlook:
MAPI error is prompted in cases when Outlook is uninstalled before the exportation of emails was complete. In such scenarios, install MS Outlook first and then try to export the emails again from the Outlook Express Program. This can stop the MAPI error from prompting up.
Change MAPI settings:
Another potential solution to this issue is changing the MAPI settings. Configure Outlook Express as the default MAPI client i.e. Messaging Application Programming Interface Client. Here is how to do it:
Open Outlook Express after restarting your system.
Click on Options on the Tools menu
Open internet properties from the change option in the connection tab.
Click any other email client other than Outlook Express on the programs tab.
Click apply and then click OK.
After clicking OK one final time, exit Outlook Express and restart the application.
Install Windows Live Mail:
If MS Outlook is not installed in your system, try installing Windows Live Mail as an alternative. This program allows its users to access, read and compose emails even without an internet connection.
If the listed solutions are unable to solve the MAPI error in Outlook Express, there are other programs available that help in repairing the damaged DBX files that might be causing the problem.
Another option is to choose a more efficient, up to date mailing client that can provide a better mailing experience. You can also contact Outlook Support Phone Number +1(844)-539-9831.