When you click E-mail Page in Microsoft OneNote 2010 to send your OneNote page as an email message in Microsoft Outlook 2010, the page is attached to the email message as an .mht file.
This problem occurs when the string value for Outlook 2010 is longer than any other program's string value in the RegisteredApplications key in the registry.
To work around this problem, use one of the following methods.
Method 1: Edit the registry
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
Add a new string value in the RegisteredApplications key that is longer than 22 characters. To do this, follow these steps:
Click Start, click Run, type regedit, and then click OK.
Locate and then click to select the following registry key: