DomainKeys Identified Mail (DKIM) is an email authentication system used to confirm that an e-mail message has been sent by an authenticated mail server or individual. A digital signature is added to the header of the message using a private cryptographic key. When the email is received, a public key that is available in the global Domain Name System is used to verify who actually sent it and if its content has been modified in any way. The chief function of DKIM is to avert the widely spread scam and spam messages, as it makes it impossible to fake an email address. If a message is sent from an address claiming to belong to your bank, for instance, but the signature doesn’t correspond, you will either not receive the message at all, or you’ll receive it with a warning that most likely it’s not an authentic one. It depends on mail service providers what exactly will happen with an email which fails the signature check. DomainKeys Identified Mail will also offer you an added protection layer when you communicate with your business associates, for example, since they can see for themselves that all the messages that you send are legitimate and have not been modified in the meantime.