'How do I check for the presence of a valid email (digital) signature attached to an Outlook MailItem (email message)?

Is there any way to

  1. Retrieve a digital signature attached to a MailItem using VBA?
  2. Verify its validity using VBA?

I'm pretty much limited to VBA in this regard. I've tried inspecting the Sender and MailItem objects but I can't see anything about a Signature object.

vbaemailoutlook


Solution 1:[1]

Outlook always represents signed/encrypted messages as regular "IPM.Note MailItem" objects. It goes as far as returning a fake IMessage MAPI interface from the MailItem.MAPIOBJECT property.

You can see this in OutlookSpy (I am its author) - select a signed message, click IMessage button on the OutlookSpy ribbon. PR_MESSAGE_CLASS will be IPM.Note. Select the PR_ENTRYID property, right click, select IMAPISession::OpenEntry. You will get back the real message with PR_MESSAGE_CLASS = IPM.Note.SMIME.MultipartSigned. You can see the attachment that contains the data.

You are pretty much limited to Extended MAPI (C++ or Delphi only) or Redemption (I am its author - any language - it wraps Extended MAPI) if you want to distinguish signed/encrypted message from the regular ones. Redemption exposes RDOEncryptedMessage object. You can retrieve it from RDOSession.GetMessageFromID using the entry id retrieved from MailItem.EntryID property in OOM.

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