S/Mime can be used to encrypt email and it can also be used by the sender to provide his digital signature so that the recipient is able to confirm the authenticity of the sender.
Why then do we still need to have DKIM implemented on top of S/Mime in certain cases. I do understand that DKIM is used to authenticate the domain but isn't a digital signature of the user via s/mime a more stronger form of authentication?
I would also appreciate if as an answer someone can explain the flow of how DKIM can be implemented on top pf S/mime (The order in which the encryption and decryption steps happens).