DomainKeys Identified Mail (DKIM) is an email authentication system used to verify that an email message has been sent by an authorized server or person. An e-signature is attached to the header of the email by using a private key. When the email is received, a public key that is available in the global DNS database is used to validate who exactly sent it and if the content has been modified in any way. The primary purpose of DKIM is to obstruct the widely spread scam and spam emails, as it makes it impossible to forge an email address. If an email message is sent from an address claiming to belong to your bank, for example, but the signature does not correspond, you will either not get the email message at all, or you’ll get it with a warning alert that most likely it’s not genuine. It depends on email providers what exactly will happen with an email message that fails the signature test. DomainKeys Identified Mail will also give you an extra layer of security when you communicate with your business associates, for example, as they can see that all the e-mails that you exchange are authentic and haven’t been modified in the meantime.