DomainKeys Identified Mail (DKIM) is an authentication system used to confirm that an e-mail message has been sent by an authenticated email server or individual. An e-signature is added to the header of the email message using a private cryptographic key. When the message is received, a public key that is available in the global DNS database is used to check who exactly sent it and if the content has been changed in some way. The fundamental job of DKIM is to stop the widely spread spam and scam messages, as it makes it impossible to forge an email address. If an email is sent from an email address claiming to belong to your bank, for example, but the signature does not match, you will either not get the message at all, or you’ll receive it with a warning that most probably it is not a genuine one. It depends on mail service providers what exactly will happen with an email which fails the signature check. DKIM will also provide you with an added layer of protection when you communicate with your business partners, for instance, since they can see that all the e-mail messages that you exchange are legitimate and haven’t been tampered with in the meantime.