Email has an important role in carrying information securely from, say your bank or your doctor to you. Much ingenuity – usually your bank giving some part of your account number – goes into ‘proving’ that the message comes from the sender it claims to be from.
Much of the problem of electronically signing emails, so that the sender and recipient can identify each other, and encrypting them, so that only the recipient can read them, has be solved for thirty years. Although Pretty Good Privacy is not perfect, it is better than individual senders trying to invent their own solutions.