DomainKeys Identified Mail, or DKIM, is a method for checking the legitimacy of an email message by using an e-signature. When DomainKeys Identified Mail is activated for a given domain, a public cryptographic key is published to the global DNS 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 email is delivered, that signature is authenticated by the incoming POP3/IMAP server using the public key. Thus, the receiver can easily discern if the message is authentic or if the sender’s email address has been forged. A mismatch will appear if the content of the email has been edited in the meantime as well, so DomainKeys Identified Mail can also be used to ensure that the sent and the delivered emails are identical and that nothing has been attached or erased. This email authentication system will increase your email security, since you can verify the legitimacy of the important email messages that you receive and your colleagues can do likewise with the messages that you send them. Depending on the given mail service provider’s policies, a message that fails to pass the test may be erased or may enter the recipient’s mailbox with a warning sign.