DomainKeys Identified Mail (DKIM) is an email authentication system used to certify that an email has been sent by an authenticated mail server or individual. An e-signature is added to the email message’s header using a private cryptographic key. When the email is received, a public key that is available in the global DNS database is used to verify who actually sent it and if its content has been edited in some way. The essential task of DKIM is to hinder the widely spread spam and scam 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 receive the email at all, or you will get it with a warning alert that most likely it is not a legitimate one. It depends on email service providers what exactly will happen with an email message that fails to pass the signature check. DKIM will also give you an added layer of security when you communicate with your business partners, for instance, since they can see for themselves that all the e-mails that you exchange are legitimate and have not been meddled with on their way.