DomainKeys Identified Mail (DKIM) is an email authentication system used to certify that an email has been sent by an authorized individual or email server. A digital signature is attached to the header of the email message 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 validate who actually sent it and if the content has been altered in any way. The fundamental function of DomainKeys Identified Mail is to block the widely spread scam and spam email messages, 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 instance, but the signature does not match, you will either not get the message at all, or you’ll receive it with a notification that most probably it’s not a legitimate one. It depends on mail service providers what exactly will happen with an email that fails the signature examination. DomainKeys Identified Mail will also supply you with an added protection layer when you communicate with your business partners, for instance, since they can see for themselves that all the e-mail messages that you exchange are legitimate and haven’t been modified on their way.