DomainKeys Identified Mail (DKIM) is an authentication system used to verify that an email message has been sent by an authenticated person or server. A digital signature is attached to the email message’s header using a private key. When the email is received, a public key that is available in the global DNS database is used to check who exactly sent it and if its content has been changed in any way. The principal function of DKIM is to block the widespread scam and spam messages, as it makes it impossible to forge an email address. If a message is sent from an email address claiming to belong to your bank, for example, but the signature doesn’t correspond, you will either not get the email at all, or you will get it with a warning notification that most likely it is not legitimate. It depends on mail service providers what exactly will happen with an email message which fails to pass the signature test. DomainKeys Identified Mail will also provide you with an additional layer of security when you communicate with your business associates, for example, as they can see that all the e-mails that you send are legitimate and haven’t been tampered with in the meantime.