In FortiMail, what does the term "Operation Mode" refer to?

In FortiMail, what does the term "Operation Mode" refer to?
A . The mode in which the device is powered on.
B . The mode in which the device interacts with the FortiManager.
C . The way the device processes email traffic and functions within the network.
D . The mode in which the device communicates with other mail servers using SMTP.

Answer: C