DomainKeys Identified Mail (DKIM) is an email validation system used to verify that an e-mail message has been sent by an authenticated server or individual. A digital signature is added to the header of the email using a private encryption key. When the message is received, a public key that is available in the global DNS database is used to confirm who exactly sent it and if the content has been modified in some way. The fundamental purpose of DomainKeys Identified Mail is to avert the widespread scam and spam emails, 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, for example, but the signature does not correspond, you will either not get the message at all, or you will receive it with an alert that most likely it is not a genuine one. It depends on email providers what exactly will happen with an email that fails to pass the signature check. DKIM will also supply you with an additional security layer when you communicate with your business allies, for example, as they can see for themselves that all the emails that you send are legitimate and have not been meddled with on their way.