DomainKeys Identified Mail (DKIM) is an email validation system used to certify that an email message has been sent by an authenticated individual or mail server. An electronic signature is added to the header of the message by using a private key. When the email is received, a public key that’s available in the global Domain Name System is used to validate who exactly sent it and whether the content has been modified in some way. The chief job of DKIM is to obstruct the widely spread spam and scam email messages, 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, for instance, but the signature doesn’t match, you will either not get the email at all, or you’ll receive it with a notification that most likely it’s not legitimate. It depends on mail service providers what exactly will happen with an email message which fails to pass the signature test. DKIM will also give you an extra security layer when you communicate with your business partners, for instance, since they can see that all the e-mails that you exchange are genuine and have not been tampered with in the meantime.