I'm working on WPF application in C#. Some time ago I had a problem with sending an encrypted email through the Outlook. The problem was strongly related to the encryption method - the S/MIME standard.
After that it came to my attention there's an other option for encrypting emails in the company I work for. It comes in Outlook 365 and it's called Microsoft Purview Message Encryption. It can be enabled by choosing Encrypt-Only option under Encrypt dropdown. More here and here.
I find is very suitable for my solution as it seems to be faster and eliminates problem with expired/missing recipients' certificates.
The way I was handling the encryption so far was as follows, through the OOM, setting flags in the MailItem object:
using Outlook = Microsoft.Office.Interop.Outlook;
(...)
Outlook.Application olkApp = new Outlook.Application();
Outlook.MailItem otlMail = olkApp.CreateItemFromTemplate(templateFullPath) as Outlook.MailItem;
otlMail.To = (...)
try
{
const string PR_SECURITY_FLAGS = http://schemas.microsoft.com/mapi/proptag/0x6E010003";
long prop = Convert.ToInt64(otlMail.PropertyAccessor.GetProperty(PR_SECURITY_FLAGS));
var ulFlags = 0x0;
ulFlags = (ulFlags | 0x1); // SECFLAG_ENCRYPTED
//ulFlags = (ulFlags | 0x2); // SECFLAG_SIGNED
otlMail.PropertyAccessor.SetProperty(PR_SECURITY_FLAGS, ulFlags);
}
catch (Exception ex)
(...)
try
{
otlMail.Send();
}
catch (Exception ex)
{
(...)
}
Unfortunately, with this way emails seems to stick with S/MIME. Even though I was trying to remove this kind of encryption through Outlook's options: (File -> Options -> Trust Center -> Email Security -> delete Default Setting), so that in new email's options was only "Encrypt-Only" option (along with Do Not Forward), and hoping the Outlook will encrypt it with new feature. Bad luck. It kept coming back.
I neither can find any useful information for developers about this feature.
Can anyone help please? Is it possible to send Encrypt-Only email through Outlook Object Model or other programming means in C#?
Regards, Kris
