DomainKeys Identified Mail (DKIM) is an authentication system used to verify that an email message has been sent by an authenticated mail server or person. A digital signature is attached to the email’s header by using a private cryptographic key. When the email message is received, a public key that is available in the global Domain Name System is used to check who exactly sent it and whether its content has been altered in any way. The chief task of DKIM is to block the widespread scam and spam emails, as it makes it impossible to forge an email address. If a 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 will get it with a notification that most likely it is not a legitimate one. It depends on email service providers what exactly will happen with an email message which fails to pass the signature check. DomainKeys Identified Mail will also provide you with an added layer of protection when you communicate with your business associates, for example, as they can see that all the e-mails that you exchange are legitimate and have not been manipulated on their way.