DomainKeys Identified Mail (DKIM) is an authentication system used to prove that an email has been sent by an authorized email server or person. A digital signature is added to the header of the message by using a private cryptographic key. When the email message is received, a public key that’s available in the global DNS database is used to verify who actually sent it and if the content has been edited in some way. The principal task of DKIM is to hinder the widely spread scam and spam email 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, for instance, but the signature doesn’t correspond, you will either not receive the email at all, or you’ll get it with an alert that most probably it’s not a legitimate one. It depends on mail service providers what exactly will happen with an email message which fails to pass the signature test. DomainKeys Identified Mail will also provide you with an extra security layer when you communicate with your business associates, for instance, since they can see for themselves that all the email messages that you exchange are legitimate and haven’t been meddled with in the meantime.