DomainKeys Identified Mail, or DKIM, is a method for validating the legitimacy of an email message using an e-signature. When DomainKeys Identified Mail is activated for a certain domain, a public cryptographic key is published to the global DNS system and a private one is stored on the email server. If a new message is sent, a signature is issued using the private key and when the message is received, that signature is authenticated by the incoming POP3/IMAP email server using the public key. Thus, the receiver can easily distinguish 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 message has been altered in the meantime as well, so DKIM can also be used to make sure that the sent and the delivered email messages are identical and that nothing has been added or removed. This email authentication system will increase your email security, since you can validate the authenticity of the important email messages that you receive and your partners can do the exact same thing with the messages that you send them. Depending on the given mail service provider’s adopted policy, an email message that fails the check may be erased or may appear in the recipient’s mailbox with a warning flag.