DomainKeys Identified Mail (DKIM) is a validation system used to certify that an e-mail has been sent by an authorized email server or person. An e-signature is added to the header of the email message using a private encryption key. When the email is received, a public key that is available in the global DNS database is used to verify who exactly sent it and if its content has been altered in some way. The chief job of DKIM is to block the widespread scam and spam messages, as it makes it impossible to forge an email address. If a message is sent from an address claiming to belong to your bank or financial institution, for example, but the signature does not correspond, you will either not get the message at all, or you will receive it with a warning note that most likely it’s not a legitimate one. It depends on email providers what exactly will happen with an email message which fails to pass the signature check. DKIM will also provide you with an extra layer of security when you communicate with your business associates, for example, as they can see for themselves that all the messages that you send are genuine and have not been tampered with on their way.