DomainKeys Identified Mail (DKIM) is an authentication system used to certify that an e-mail message has been sent by an authorized individual or email server. A digital signature is added to the message’s header using a private key. When the message is received, a public key that’s available in the global Domain Name System is used to check who actually sent it and if the content has been altered in any way. The essential task of DKIM is to block the widespread scam and spam messages, as it makes it impossible to fake an email address. If an email 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 email at all, or you’ll get it with a notification that most probably it’s not genuine. It depends on email providers what exactly will happen with an email message which fails the signature examination. DomainKeys Identified Mail will also provide you with an extra layer of protection when you communicate with your business associates, for instance, as they can see that all the e-mail messages that you send are legitimate and have not been meddled with in the meantime.