Recoverable error.
The SMTP server sends this message to the client to show that the local host cannot find an A record that corresponds to an MX record for the destination host. This is a configuration error in the domain name server.
The mail is rejected. SMTP continues.
Determine what MX records are stored in the domain name server and why SMTP cannot find a corresponding A record for one or more of the MX records. Tell the domain name server administrator about the error.
SMTPRES
ProcessRQR