Method and system for replacing sent mail system cluster

The invention relates to a method for replacing a sent mail system cluster. A terminal, a DNS, a mail server and MX records are included; a process of sending a mail by a mail system cluster is included; the process comprises the steps that: A, the terminal initiates a request for sending a mail; B, the terminal requests the DNS for the MX records through the address suffix of an addressee; and, if the MX records exist, the mail server appointed by the MX records is located; C, multiple items of DNS records and MX records are established through the DNS; and the DNS analyzes out multiple IP addresses; D, the mail server uses a virtual sub-network card, so that the analyzed multiple IP addresses are configured on the mail server; E, the DNS analyzes the MX records on the mail server in a polling manner; and F, strategy routing is added in a routing level; the IP addresses analyzed by the DNS in the polling manner are appointed as source IPs in a forced manner; and the mail is forwardedby the source IPs. By mea