| 摘要 |
A network 1 comprises personal computers 2 and an email exchange server 3 linked through a computer networking device 4. Primary, ADSL connection 6 to the Internet is provided via an Internet Service Provider (ISP) 7 and a transceiver 5. A secondary connection 9 provides wireless access to a second ISP 11 in event of failure of the primary connection. A Domain Name System (DNS) 12 associates the domain name of the email server 3 with the IP address of a forwarding email server 13 and also stores the IP address of each of the primary and secondary connections in association with the domain name of the email server 3 in an MX record. When a 3rdparty email server 13 wishes to send an email to email server 3, the DNS returns the IP address of the forwarding email server 13 and the email is transferred to this server. A register 15 stores the IP address of each of the primary and secondary connections and provides the forwarding server with the IP address of the preferred connection when queried therefrom such that the forwarder may attempt to transfer the email to email server 3 via the primary connection. The register provides the forwarding server with the IP address of the secondary connection if the initial email transfer fails. Since the DNS stores the IP addresses of the primary and secondary connections, it is able to successfully verify the email server via reverse lookup when the email server 3 attempts to lookup the IP address of a 3rdparty email server 13. Both the primary and secondary connections have public static IP addresses and the latter address is provided via a SIM card which enables a Mobile Subscriber Identity to be recognised by the network infrastructure 11 as being associated with a specific IP address which can be accessible outside the wireless network.
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