DomainKeys Identified Mail (DKIM) is an email validation system used to check that an email message has been sent by an authenticated mail server or individual. A digital signature is added to the header of the message using a private key. When the message 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 altered in some way. The essential function of DKIM is to hinder the widespread scam and spam 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 or financial institution, for instance, but the signature does not match, you will either not receive the email at all, or you’ll receive it with a warning note that most probably it is not legitimate. It depends on mail service providers what exactly will happen with an email message which fails the signature check. DomainKeys Identified Mail will also give you an additional protection layer when you communicate with your business allies, for instance, as they can see for themselves that all the emails that you exchange are legitimate and have not been modified on their way.