Email spoofing. sketchycorp runs an smtp server and has experienced a spoofing attack.

(a) name three web or command-line tools attackers could have used to conduct the attack?
(b) sketchycorp has implemented vanilla smtp, which does not provide authentication, confidentiality, or integrity. explain how each of the following mechanisms would
(i) dkim
ii) dmarc
iii) spf
(iv) starttls
(c) whatever sketchycorp does, messages that its users send to users of other email providers add one or more of these properties might still have no confidentiality. why? what could the company require its users to do to guard against this?