DomainKeys Identified Mail (DKIM) is an email authentication system used to check that an e-mail message has been sent by an authenticated individual or mail server. A digital signature is added to the header of the email by using a private cryptographic key. When the email message is received, a public key that’s available in the global DNS database is used to validate who exactly sent it and whether the content has been changed in some way. The chief job of DomainKeys Identified Mail is to hamper the widespread spam and scam email 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 correspond, you will either not receive the email message at all, or you will get it with a notification that most probably it is not authentic. It depends on email service providers what exactly will happen with an email message that fails the signature examination. DKIM will also offer you an additional layer of security when you communicate with your business partners, for example, as they can see for themselves that all the emails that you exchange are authentic and haven’t been modified in the meantime.