DomainKeys Identified Mail, or DKIM, is a method for checking the legitimacy of an email using an electronic signature. When DomainKeys Identified Mail is activated for a certain domain name, a public key is published to the global Domain Name System and a private one is kept on the mail server. When a new email message is sent, a signature is issued using the private key and when the message is delivered, the signature is checked by the POP3/IMAP server using the public key. In this way, the recipient can easily distinguish if the email message is genuine or if the sender’s email address has been forged. A mismatch will appear if the content of the email message has been altered in the meantime as well, so DomainKeys Identified Mail can also be used to ensure that the sent and the received emails are identical and that nothing has been attached or erased. This email authentication system will increase your email security, as you can validate the authenticity of the important email messages that you get and your colleagues can do the same with the emails that you send them. Based on the particular email service provider’s adopted policy, an email message that fails to pass the check may be removed or may enter the receiver’s inbox with a warning notification.