When a recipient opens a CRES encrypted envelope, and chooses to forward the encrypted envelope to another recipient, which of the following devices is the SMTP client?

When a recipient opens a CRES encrypted envelope, and chooses to forward the encrypted envelope to another recipient, which of the following devices is the SMTP client?

A.
The first recipients mail server.

B.
The CRES server.

C.
The mail user agent on the first recipient’s computer.

D.
The ESA that originally encrypted the message.