Msimn.exe is the main Outlook Express program file. When there is an error
message that refers to this file, it will usually quit, and Outlook Express will
not start.
See Q225096 article from the Microsoft Knowledge base
To work around this issue:
1. Disconnect from the Internet, and then start Outlook Express. If you are
prompted to establish a Dial-Up Networking connection, click Cancel.
2. On the Tools menu, click Message Rules, and then click Mail.
3. Find the rule that is configured with either or both of the following
actions, and then click to clear the check box next to it:
- Do not Download it from the server
- Delete it from Server
4. Click OK.
For additional information about these error messages,click the article number
below to view the article in the Microsoft Knowledge Base:
Q233264 Error Message If the Folders.dbx File Is Missing or Damaged