DomainKeys Identified Mail (DKIM) is an email authentication system used to certify that an email has been sent by an authorized mail server or individual. An electronic signature is attached to the email’s header by using a private key. When the email is received, a public key that’s available in the global DNS database is used to check who actually sent it and if its content has been modified in any way. The chief purpose of DomainKeys Identified Mail is to block the widely spread spam and scam emails, as it makes it impossible to forge an email address. If a message is sent from an address claiming to belong to your bank or financial institution, for instance, but the signature doesn’t correspond, you will either not receive the email message at all, or you will get it with an alert that most probably it is not an authentic one. It depends on email providers what exactly will happen with an email which fails to pass the signature examination. DomainKeys Identified Mail will also offer you an additional layer of security when you communicate with your business allies, for example, as they can see for themselves that all the e-mails that you send are legitimate and haven’t been meddled with in the meantime.