＞ 0Key… ＜
＞ After some research ＜
...I realized that this I should have done creating a section with "String" here:
Microsoft Outlook will automatically block some attachments which it detects potentially unsafe. For example, your friend sent you an attachment of an .exe file, when you open the email via Outlook, the attachment is blocked and invalid, and you can only see a warning sentence in the message header. See following screen shot. In this article, I will introduce a guidance to access blocked attachments in Microsoft Outlook.
To access blocked attachments which Outlook thinks potentially unsafe in Outlook, you can do as following:
Step 1: Open the Run dialog box with pressing the Win + R keys in a meanwhile, enter the regedit in the Open box, and then click the OK button.
Step 2: In the popping up User Account Control dialog box, click the Yes button.
Step 3: Now you get into the Registry Editor window, open the Security folder with following paths:
Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security
Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security
Outlook 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Security
Step 4: Click the Edit > New > String Value in the Registry Editor Window, and then name the new string as Level1Remove.
Step 5: Double click the new string of Level1Remove, then enter the file extended name in the Value data box, and click the OK button.
For example, you want to access blocked attachments of .exe files, just enter the .exe into the Value data box.
Note: To unblocked several kinds of files, just enter all of their extended names into the Value data box, and separate each extended name with semicolon (;), such as .exe; .msi
Step 6: Close the Registry Editor Window, and restart your Microsoft Outlook.
Then you will see the blocked attachment is unblocked, and you can access the unblocked attachment easily. See the following screen shot: