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Outlook Express: The message was not sent (0X800C0131)

Issue
Solution

Issue

During the launch of Outlook Express, you receive the following error message:

An unknown error has occurred. Protocol: SMTP, Port: 0, Secure SSL: No, Error 0x800c0131

This problem may be due to an absence or corruption of Folders.dbx file.

Solution

Restore the file Folders.dbx.

Then locate the file Folders.dbx through the search tool of Windows (Start / Search / Files or Folders).

Rename the file to make a backup, for example Folders.back.

Launch Outlook Express.

Folders.dbx file will automatically be recreated and the application will open correctly.