Error message when you try to open a link that has an .xnk file name extension in Outlook 2007: “Cannot open file”

In Microsoft Office Outlook 2007, you try to open a link to a Microsoft Exchange Server public folder shortcut that has an .xnk file name extension. When you do this, you may receive an error message that resembles one of the following error messages:

• Cannot open file
• The command line argument is not valid. Verify the switch you are using.

This behavior occurs because of increased security in Outlook 2007. By default, Outlook 2007 denies access to these files.

Warning This workaround may make a computer or a network more vulnerable to attack by malicious users or by malicious software such as viruses. We do not recommend this workaround but are providing this information so that you can implement this workaround at your own discretion. Use this workaround at your own risk.

To work around this behavior, create a link association between the .xnk file name extension and Outlook 2007. To do this, follow these steps.

Important You should open or download only those .xnk files that are sent by a known source.

1. Click Start, click Run, type Explorer in the Open box, and then click OK.
2. On the Tools menu, click Folder Options.
3. In the Folder Options dialog box, click the File Types tab, and then click New.
4. In the Create New Extensions dialog box, type xnk in the File Extension box, and then click OK.
5. Click to select XNK under Registered file types, and then click Advanced.
6. In the Edit File Type dialog box, type XNK next to the icon, and then click New.
7. In the New Action dialog box, type OPEN for Action, and then type the following text under Application used to perform action:
   "DriveLetter:\path\Outlook.exe" /x "%1"
   Click OK two times.
   
   Note By default, the path of the Outlook.exe file is as follows:
   "C:\Program Files\Microsoft Office\OFFICE12\Outlook.exe" /x "%1"
8. Click Close.

This behavior is by design.