DomainKeys Identified Mail (DKIM) is an email authentication system used to confirm that an email message has been sent by an authenticated email server or individual. An e-signature is attached to the header of the email by using a private key. When the message is received, a public key that’s available in the global DNS database is used to validate who actually sent it and if its content has been modified in any way. The fundamental task of DomainKeys Identified Mail is to impede the widespread spam and scam emails, as it makes it impossible to fake an email address. If a message is sent from an email address claiming to belong to your bank or financial institution, for instance, but the signature does not correspond, you will either not receive the message at all, or you’ll receive it with an alert that most probably it is not an authentic one. It depends on email service providers what exactly will happen with an email that fails to pass the signature examination. DKIM will also offer you an additional security layer when you communicate with your business associates, for instance, as they can see that all the e-mails that you exchange are genuine and have not been modified in the meantime.