What can Blane use to accomplish this?

Blane is a security analyst for a law firm. One of the lawyers needs to send out an email to a client
but he wants to know if the email is forwarded on to any other recipients. The client is explicitly
asked not to re-send the email since that would be a violation of the lawyer’s and client’s
agreement for this particular case. What can Blane use to accomplish this?

A.
He can use a split-DNS service to ensure the email is not forwarded on.

B.
A service such as HTTrack would accomplish this.

C.
Blane could use MetaGoofil tracking tool.

D.
Blane can use a service such as ReadNotify tracking tool.