By default, the Helo property indicates the name of the host, who sends the message. As a result, the receiver-SMTP will not have to perform MX resolution on this name in order to validate the HELO parameter. The HELO receiver MAY verify that the HELO parameter really corresponds to the IP address of the sender. However, the receiver MUST NOT refuse to accept a message, even if the sender's HELO command fails verification.