Symptoms
If you use the Encrypting File System (EFS) to secure the Outlook Secure Temporary File folder, you are unable to save email attachments to a network share or to an external memory device that is not encrypted or does not support encryption. When you attempt to do this, the following error message is displayed:
Cannot save the attachment.
Note EFS is not available on non-NTFS formatted devices. For example, if the target location is formatted using FAT32, you may experience the symptom described above.
Cause
When you open file attachments that are considered safe, Outlook 2010 and Outlook 2007 put these attachments in a subdirectory of the Temporary Internet Files directory as an additional precaution. If that subfolder is encrypted using EFS, files in it cannot be copied to network shares or external memory devices that are not encrypted.
Resolution
When the following registry value explained below is set, Outlook will allow email attachments to be copied to network shares or external memory devices (e.g. USB memory drive) that are not encrypted with EFS. 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
Outlook 2010
To have Outlook 2010 allow email attachments to be saved to non-EFS encrypted file locations, create and configure the EnableCopyFromEFS registry entry. To do this, follow these steps:
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Start Registry Editor.
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In Windows Vista or Windows 7, click Start
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In Windows XP, click Start, click Run, type regedit in the Open box, and then click OK.
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Locate and then click the following registry subkey:
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Options\Attachments
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On the Edit menu, point to New, and then click DWORD Value.
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Type EnableCopyFromEFS, and then press ENTER.
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Right-click EnableCopyFromEFS, and then click Modify.
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In the Value data box, type 1, and then click OK.
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Exit Registry Editor.
Workaround
You can use the Copy command to copy the email attachment to the Windows Clipboard, then Paste it into the desired location. Alternately, you can drag and drop the attachment to the desired location.
More Information
By default, the Outlook Secure Temporary File subfolder has a randomly-generated name and is located in the following path:
C:\Users\<Alias>\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Outlook
