DomainKeys Identified Mail (DKIM) is an email authentication system used to certify that an email has been sent by an authenticated mail server or person. A digital signature is added to the header of the message using a private key. When the message is received, a public key that’s available in the global Domain Name System is used to verify who exactly sent it and if the content has been edited in some way. The prime task of DomainKeys Identified Mail is to prevent the widespread spam and scam messages, as it makes it impossible to fake an email address. If an email is sent from an email address claiming to belong to your bank or financial institution, for instance, but the signature doesn’t match, you will either not get the email message at all, or you’ll get it with an alert that most probably it’s not a legitimate one. It depends on email service providers what exactly will happen with an email which fails the signature check. DKIM will also provide you with an additional protection layer when you communicate with your business associates, for example, as they can see for themselves that all the e-mail messages that you exchange are authentic and have not been modified in the meantime.