Smart host
Encyclopedia
A smart host is a type of mail relay server which allows an SMTP
server to route e-mail
to an intermediate mail server rather than directly to the recipient’s server. Often this smart host requires authentication from the sender to verify that the sender has privileges to have mail forwarded through the smart host. This is an important distinction from an open relay that will forward mail from the sender without authentication. Common authentication techniques include SMTP-AUTH and POP before SMTP
.
) a smart host configuration will accept mail on behalf of the primary mail server if it were to go offline. When the primary mail server comes back online
, mail is subsequently delivered via the smart host.
, in an effort to reduce e-mail spam
originating at their customer’s IP address
es, will not allow their customers to communicate directly with the recipient’s mail server via the default SMTP port number 25. In this case the customer has no choice but to use the smart host provided by the ISP.
ISPs involved in this practice include:
Rogers Cable
Shaw Communications
Eircom.net
When a host runs its own local mail server, a smart host is often used to transmit all mail to other systems through a central mail server. This is used to ease the management of a single mail server with aliases, security, and Internet access rather than maintaining numerous local mail servers.
Simple Mail Transfer Protocol
Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission across Internet Protocol networks. SMTP was first defined by RFC 821 , and last updated by RFC 5321 which includes the extended SMTP additions, and is the protocol in widespread use today...
server to route e-mail
E-mail
Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...
to an intermediate mail server rather than directly to the recipient’s server. Often this smart host requires authentication from the sender to verify that the sender has privileges to have mail forwarded through the smart host. This is an important distinction from an open relay that will forward mail from the sender without authentication. Common authentication techniques include SMTP-AUTH and POP before SMTP
POP before SMTP
POP before SMTP or SMTP after POP is a method of authorization used by mail server software which helps allow users the option to send e-mail from any location, as long as they can demonstrably also fetch their mail from the same place....
.
Use for backup mail (secondary MX) services
When configured to be a backup mail server (not the primary MX recordMX record
A mail exchanger record is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available...
) a smart host configuration will accept mail on behalf of the primary mail server if it were to go offline. When the primary mail server comes back online
ONLINE
ONLINE is a magazine for information systems first published in 1977. The publisher Online, Inc. was founded the year before. In May 2002, Information Today, Inc. acquired the assets of Online Inc....
, mail is subsequently delivered via the smart host.
Use in spam control efforts
Some ISPsInternet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
, in an effort to reduce e-mail spam
E-mail spam
Email spam, also known as junk email or unsolicited bulk email , is a subset of spam that involves nearly identical messages sent to numerous recipients by email. Definitions of spam usually include the aspects that email is unsolicited and sent in bulk. One subset of UBE is UCE...
originating at their customer’s IP address
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
es, will not allow their customers to communicate directly with the recipient’s mail server via the default SMTP port number 25. In this case the customer has no choice but to use the smart host provided by the ISP.
ISPs involved in this practice include:
Rogers Cable
Rogers Cable
Rogers Cable Inc., a subsidiary of Rogers Communications Inc., is Canada's largest cable television service provider with about 2.25 million television customers, and over 930,000 Internet subscribers, in Manitoba, Southern & Eastern Ontario, New Brunswick and Newfoundland and Labrador.The...
Shaw Communications
Shaw Communications
Shaw Communications is Canada's largest telecommunications company that provides telephone, Canada's fastest Internet and television services as well as broadcasting and soon Wifi. Shaw is headquartered in Calgary, Alberta...
Eircom.net
When a host runs its own local mail server, a smart host is often used to transmit all mail to other systems through a central mail server. This is used to ease the management of a single mail server with aliases, security, and Internet access rather than maintaining numerous local mail servers.