GB2463047A

GB2463047A - Providing a wireless e-mail backup link for when an ADSL or primary internet mail link is unavailable

Info

Publication number: GB2463047A
Application number: GB0815777A
Authority: GB
Inventors: David Richard Gardner
Original assignee: Datel Solutions Ltd
Current assignee: Datel Solutions Ltd
Priority date: 2008-09-01
Filing date: 2008-09-01
Publication date: 2010-03-03
Also published as: GB2462939B; GB0915155D0; GB2462939A; WO2010023330A1; GB0815777D0

Abstract

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.

Description

An Email Communications System The following invention is of particular relevance to local networks which use an internal mail server.

Fig 1 illustrates a schematic representation of a prior art email communication system having a local network 1 comprising a number of personal computers 2 and an internal email exchange server (mail transfer agent) 3 linked through a computer networking device 4.

Commonly networks 1 are connected to the internet to allow access to the worldwide web and enable emails to be sent and received to/from computers located outside the local network.

Connection to the internet may be provided via a wired link such as a Digital Subscriber Line (DSL and typically an Asymmetric DSL) 6 to an internet service provider (ISP) 7. Data is sent from and received by the network 1 through a DSL transceiver 5. Connection 6 is assigned a unique static IP address. By virtue of this, email server 3 has a corresponding address. A domain name server DNS 8, holds a number of records associated with the domain name including, a record of the domain name and the associated IP address of the email server 3 (Address A' Record) and a second record comprising the domain name and the host name of the email server 3 (MX record). Each MX record also contains an indication of the priority of the server relative to any other servers which receive mail for the domain. Commonly a domain name is served by multiple mail servers, the additional servers acting as backups in case the primary server fails. Where there are multiple servers, the DNS keeps an A' record and a MX record for each server.

The DNS 8 may be held by the ISP 7 by a 3' party or where the network is large by the network itself. However, the present invention is thought to be most applicable to systems of the first two instances.

Emails received from a PC 2 which are addressed to another PC 2 in the same network 1 can be handled internally within the network 1 by the internal email server 3. When the server 3 receives an email from a PC 2 addressed to a domain which is not served by the internal email server 3, e.g. to a computer 2A outside of the network, the server 3 needs to obtain the IP address of the email server 3A which will accept emails for that specific domain. To achieve this, the email server 3 queries the local domain name server DNS 8. The DNS 8 subsequently returns (usually after querying through the domain name system other local and higher DNSs) the IP address (from the A record) and the host name (from the MX record) of the email server 8 which will accept emails for the specific domain. The email server 3 then tries to establish a connection with the mail server 3A and sends the email via the simple mail transfer protocol (SMTP).

In order for the internal email server 3 to be able to receive emails sent from outside the network, it is generally necessary for IP address of the network's transceiver 5 to the internet to be static. By static it is meant that the transceiver 5 is assigned the same address each time it is initiated. It is also necessary that the DNS holds the MX record and A' record for the email server 3 (and any additional servers) so that queries from for the IP address of domain's email server can be resolved.

As a safeguard against sending unsolicited mail, the DNS 8 will often conduct a reverse DNS lookup'. For each email sever 3, the DNS also holds a third record (PTR) which holds an IP address and a corresponding domain name (similar to the A' record but in reverse). When a reverse DNS lookup is performed, the DNS obtains the IP address of the connection from which the query was made and the domain name from which the query purports to come from, retrieves the appropriate PTR record and checks the domain name in the record against the domain from which the query is purported to come. A match indicates that the query is from a genuine source and the DNS will answer the query.

In order to provide a continued internet connection during a disruption of the DSL line 6, it is possible to provide a second, wireless connection 9. To effect this, the network 1 is provided with a wireless transceiver 10 which communicates via a base station to the network operator who provide the internet connection and effectively act as a ISP 11. Both the DSL and wireless transceivers 5, 10 may be contained within a single unit and are commonly sold commercially incorporated with other hardware/software such as firewalls as a ADSL/3G routers. Suitable routers are available under names "Billion," a trade mark of Billion Electric Co., Ltd and "Draytek," a registered trade mark of DrayTek Corp.. The wireless connection 9 between the wireless transceiver 10 and the ISP 11 is assigned a dynamic IP address by the network operator 11, i.e. in that a new IP address is assigned to the connection 9 each time it is initiated. The address may also change at intervals when the connection 9 is refreshed. Additionally, because the access to the internet runs via the network operator's 11 network, the IP addresses of the connection 9 is not known or recognised outside of the wireless network, e.g. by the DNS 8.

A mechanism may also be put in place to automatically initiate the wireless connection 9 on sensing that the DSL connection 6 has failed.

The above described system, however, does not allow the effective sending and receiving of emails when the network's connection to the internet is via the wireless link 9.

When, through connection 9, the email server 3 makes a query to the DNS 8 for the relevant information of an email server for a domain, a reverse DNS lookup will indicate that the IP address of the email server 3 is not the same as that in its PTR record, and will therefore refuse to provide the necessary MX' or A' records preventing the email from being sent.

Equally, an outside email server 9 wanting to send an email to the email server 3, will be given, from the DNS 8, the IP address of the connection through the non-ftinctioning DSL line 6.

The present invention was devised with the intention to enable email to be sent and received when the primary connection is disrupted or cut off There is provided an email communications system comprising a network having a domain name, an exchange server and a first connection to the internet characterised by: a second, wireless connection to the internet, the first and second connections having respective first and second public static IP addresses; a register holding the addresses of the two connections; and means for selecting one of the addresses and sending an email addressed to the domain via the selected address.

By assigning the email exchange server two public static IP addresses through either the first or second wireless connection, emails can be still be sent to the exchange server in the advent that one of the connections is interrupted or fails.

Preferably the register also contains an indication of the priority of the connections and the means for selecting one of the addresses, selects in preference the address which is indicated as having the higher priority. This enables emails to be preferably directed through the first connection unless it becomes interrupted, whereby emails will then be sent via the second connection.

It is also preferred that the system comprises an email forwarder hosted outside of the network and having a third IP address. The DNS registry of the domain name provider can be amended so that email queries for the domain are directed to the email forwarder. The email forwarder comprises a means to store emails sent to it from 3'' party email servers, and a DNS register holding MX records corresponding to the first and second connections, means for selecting one of the addresses and means for forwarding the email addressed to the email server via the selected address.

Additionally the system may also comprise a router which switches between connections in response to a loss of one connection.

The invention will now be described by way of example with reference to Figure 2.

Figure 2 illustrates a local network 1 having an email server 3 adapted to receive and send emails to and from a domain having a registered domain name. The network is connected to the internet via ISP 7 through an ADSL connection 6 by transceiver 5.

The ADSL connection 6 is provided with a first public static IP address. A second auxiliary connection 9 to the internet is provided through a wireless network (though not necessarily with handover capabilities) via a second ISP 11. Connection 9 is provided with a second public static IP address. This is achieved by providing the wireless transceiver 10 with a Mobile Subscriber Identity (held on a Subscriber Identity Module (SIM)) recognised by the network infrastructure 11 as being associated with a specific IP address which can be accessible outside the wireless network, Suitable SIM cards can be obtained from Vodafone� of Vodafone House, The Connection, Newbury, Berkshire, RG14 2FN, England and are compatible with most wireless routers, including 3G routers.

The system further comprises a local domain name server 12, email server 13 having a third public static IP address, store 14 and register 15.

The DNS 12 acts to serve queries from email server 3. The DNS has a registry (not shown) with a number of records associated with the domain name including a record comprising the domain name and the IP address of server 13, a record comprising the domain and hostname of the email server 13 and a third and fourth records comprising the IP address for each connection 6 and 9 with the domain name.

Register 15 holds a record of the domain name, the IP addresses of the email server as assigned through the ADSL connection 6 and the wireless connection 9, the hostname of the email server, an indication of the preference of these two connections.

When in use, a third party mail server 3A, wanting to send an email to an address within the domain served by the internal email network 3, will query via the domain name system the local DNS 12. DNS 12 will return from its own register (not shown) the hostname and IP address of the email forwarder 13. The 3i party server 8 will establish a connection with the email forwarder 13 and send the email via SMTP.

The forwarder 13 receives the email and stores it in store 14. The forwarder 13 takes an email from the store 14, identifies from the email the intended domain name of the email, and interrogates register 15 for the IP address and host name of the email server 3 indicated from the priority indication as being the most preferable. The email forwarder 13 then attempts to establish a connection to email server 3 via connection 6. Should the email forwarder 13 be unable to communicate to the email server 3 through connection 6 because, for example, the ADSL connection has been interrupted or failed, the email forwarder 13 will interrogate the register for the IP address associated with the second connection and attempt to send the email via the second IP address corresponding to the wireless connection.

When email server 3 receives an email from a PC 1 addressed to a domain which it does not serve, it sends a query to the DNS 12 via either the wired 6 or wireless connection 9. The DNS checks the IP address of the source of the request against its PTR record for that IP address which will indicate that the IP address is associated with the domain name of the server. As the domain name of the source match the domain held in the PTR record, the DNS will answer the request.

The services provided by the DNS 12, email forwarder 13, store 14 and registry 15 and their arrangement there between are obtainable through ZoneEdit � Inc., P.O.Box 821067, Vancouver, WA 98682 (owned by Dotstar Inc.).

It will be appreciated that the above is only an example and that the claimed system encompasses many variations on the above. For example, an alternative system may not comprise the email forwarder 13. The DNS 12 could be arranged to interrogate register 15 which will also hold the PFT records. The DNS would be to supply The system could also contain other modifications, i.e. firewalls and mail relays.

The ADSL connection 6 may be replaced by any other type connection including other DSL connections, dial-up, cable, fibre optic or wireless.

Claims

Claims 1. An email communications system comprising a network having a domain name, an email exchange server and a first connection to the internet characterised by: a) a second, wireless connection to the internet, the first and second connections having respective first and second public static IP addresses; b) a register holding the addresses of the two connections for the domain name; and c) means for selecting one of the addresses and sending an email addressed to the exchange server via the selected address.
2. An email communications system according to claim 1 wherein the register also contains and indication of the priority of the connections and the means for selecting one of the addresses, selects in preference the address which is indicated as having the higher priority.
3. An email communication system in which emails addressed to the domain name are directed to and stored by an email forwarder having a third IP address.
4. An email communications system according to any previous claim comprising a router which switches between connections in response to a loss of one connection.
5. An email communications system substantially as described above or illustrated in Figure 2.Amendments to the claims have been filed as follows: Claims 1. An email communications system comprising a network having a domain name, an email server and a first connection to the internet, the email communications system chara cterised by: a) a second, wireless connection to the internet, the first and second connections having respective first and second public routable static IP addresses; b) a domain name server which can communicate with the email server through either the first or second connections to the internet, the domain name server having a register holding the addresses of the two connections, and an indication of the priority for each of Q the connections; and Co. c) the domain name server having means, upon being queried for an address for use to send an email to the email server, to select and Q 15 return one of the addresses held in the register based on the indication of priority of the connections..2. An email communications system according to claim 1 wherein the domain name server selects in preference the address corresponding to the first connection to the internet.3. An email communications system according to any previous claim wherein the network comprises a router which switches between connections in response to a loss of one connection.4. An email communications system substantially as described above or illustrated in Figure 2.