Outlook 2k7 Integration (via P/Invoke) - Blocking unsafe attachments

Question

We're currently developing a plug-in for a piece of software in C#. This plug-in extracts the contents of a PST file and stores all items in it as text files (with the exception of attachments, which are stored as their type in the same folder as the email).

It has been working without issue until we tested it on Windows 7 w/ Outlook 2K7. After running the same previous job on a machine with Outlook 2000 on it, we noticed that there were over 12,000 files missing. These files turned out to be attachments (mostly URLs)

We found that the issue is that Outlook 2K7 blocks attachments with specific extensions. If you open the email in Outlook itself, you see a blue bar at the top stating "Outlook blocked access to the following potentially unsafe attachments" and all the attachments in the emails.

Is there a way to programmatically get these attachments without Outlook blocking them?

The code we use to save the attachments is:

private void saveAttachment(ref object oEmail, StoreInfo currentStoreInfo, string sEmailID, string sExportPath)
{

   int iAttachCount = 0;
   object oAttach = null;
   oAttach = getNextAttachment(oEmail, ref iAttachCount);

   while (oAttach != null)
   {
      saveAttachment(sEmailID, sExportPath, oAttach);
      oAttach = getNextAttachment(oEmail, ref iAttachCount);
   }

} 

private object getNextAttachment(object oEmail, ref  int iAttachCount)
{
   object oAttach = null;

   try
   {
      iAttachCount++;
      oAttach = GetProperty(oEmail, "Attachments", new object[] { iAttachCount });
   }
   catch //(Exception ex)
   {
      // There was no attachment to be gotten
      oAttach = null;
   }
   return oAttach;
}

Trevor Watson Trevor Watson · Accepted Answer · 2011-05-25T19:53:00

Just putting this on here in case anybody else runs into the same issue. Outlook 2K7 has a Level1 file type feature that blocks access to attachments with specific extensions.

However, you can change the registry to allow access to these files. Just remember to set it back to the way it was prior to you modifying it for security's sake.

private void SetLevel1RemoveValues()

    {
        // Get the base key for the current user HKEY_CURRENT_USER
        Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.RegistryKey.OpenRemoteBaseKey(Microsoft.Win32.RegistryHive.CurrentUser, "");
        // Get the security key from the registry
        Microsoft.Win32.RegistryKey subKey = regKey.OpenSubKey("Software\\Microsoft\\Office\\" + sCurrentOutlookVersion + ".0\\Outlook\\Security", true);

        // If the Outlook\Security key doesn't exit, create one
        if (subKey == null)
            subKey = regKey.CreateSubKey("Software\\Microsoft\\Office\\" + sCurrentOutlookVersion + ".0\\Outlook\\Security");

        // Loop through each Value in the registry to see if the Level1Remove key already exists.
        string[] sValues = subKey.GetValueNames();

        bool bHasLevel1RemoveKey = false;
        foreach (string sValue in sValues)
            if (sValue == "Level1Remove")
                bHasLevel1RemoveKey = true;

        // If the key already exists, store the data so we can reset it later
        if (bHasLevel1RemoveKey)
            sPrevLevel1RemoveValues = subKey.GetValue("Level1Remove").ToString();
        else
            sPrevLevel1RemoveValues = "";

        // Create an array of all Level 1 Extensions
        string[] level1Extensions = new string[] { ".ade", ".adp", ".app", ".asp", ".bas", ".bat", 
            ".cer", ".chm", ".cmd", ".com", ".cpl", ".crt", ".csh", ".exe", ".fxp", ".gadget", 
            ".hlp", ".hta", ".inf", ".ins", ".isp", ".its", ".js", ".jse", ".ksh", ".lnk", 
            ".mad", ".maf", ".mag", ".mam", ".maq", ".mar", ".mas", ".mat", ".mau", ".mav", ".maw", 
            ".mda", ".mdb", ".mde", ".mdt", ".mdw", ".mdz", ".msc", ".msi", ".msp", ".mst", ".ops", 
            ".pcd", ".pif", ".pfr", ".prg", ".pst", ".reg", ".scf", ".scr", ".sct", ".shb", ".shs", 
            ".tmp", ".url", ".vb", ".vbe", ".vbs", ".vsmacros", ".vss", ".vst", ".vsw", 
            ".ws", ".wsc", ".wsf", ".wsh" };

        // Set the value in the registry to the list of all Level 1 extensions so we can extract them
        subKey.SetValue("Level1Remove", string.Join(";", level1Extensions));

        // Close (and save) the values
        subKey.Close();
        regKey.Close();
    }

Outlook 2k7 Integration (via P/Invoke) - Blocking unsafe attachments

1 Answers