DomainKeys Identified Mail, or DKIM, is a system 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 DNS database and a private one is kept on the email server. If a new email message is sent, a signature is issued using the private key and when the message is delivered, the signature is verified by the incoming email server using the public key. Thus, the recipient can easily distinguish if the message is authentic or if the sender’s address has been spoofed. A discrepancy will appear if the content of the email message has been edited in the meantime as well, so DKIM can also be used to ensure that the sent and the delivered emails are identical and that nothing has been attached or deleted. This authentication system will strengthen your email security, as you can verify the authenticity of the important email messages that you get and your colleagues can do likewise with the messages that you send them. Depending on the particular email provider’s adopted policy, an email that fails the test may be removed or may show up in the recipient’s inbox with a warning.