DomainKeys Identified Mail, or DKIM, is a system for checking the genuineness of an email by using a digital signature. When DKIM is activated for a given domain, a public cryptographic key is published to the global Domain Name System and a private one is kept on the mail server. If a new email message is sent, a signature is issued using the private key and when the email message is delivered, that signature is ‘scanned’ by the incoming POP3/IMAP server using the public key. Thus, the receiver can easily know if the email message is legitimate or if the sender’s address has been spoofed. A mismatch will occur if the content of the email has been altered on its way as well, so DKIM can also be used to ensure that the sent and the received email messages are identical and that nothing has been added or removed. This email validation system will increase your email security, as you can confirm the legitimacy of the important email messages that you receive and your associates can do the same with the email messages that you send them. Depending on the particular email provider’s adopted policies, a message that fails to pass the test may be erased or may reach the recipient’s mailbox with a warning sign.