"Internet Email Routing"
How MAIL ROUTING Works?
This article presents the explanation of how mail systems on the Internet are estimated to route messages based on information from the domain system described in emails.
The procedure of directing an email to the recipients domain (host) is called routing.
The aim of this article is to describe how mailers are to decide how to route a mail addressed to a given Internet domain name. It includes a clarification of how mailers interpret MX records which are used for mail routing.
We will start with an example.
If a message was addressed to a mailbox ‘accuwebhosting.com’ that one could just open an SMTP connection to accuwebhosting.com and pass the message along. Under domains, no one can simply open a connection to accuwebhosting.com but must instead ask the domain system where messages are to be delivered and the mailer may learn that it has a choice of routes to accuwebhosting.com. This article is necessary a set of guidelines on how mailers should behave in this complex world.
E-Mail Routing and the Domain Scheme:
The domain servers accumulate the information as a series of resource records. Each record contains a particular piece of information about a given domain name. For the purpose of email routing, the system stores records known as MX records. Each MX record matches a host (domain) name with 2 pieces of data. One is the name of a host and second is preference value. Preference value is an unsigned 16 bit integer. This integer use to identify the priority when multiple MX presents.
Common Routing Strategy:
Before delving into a detailed discussion of how mailers are expected to do mail routing, it would seem to make sense to give a brief overview of how this memo is approaching the problems that routing poses.
The first major principle is derived from the definition of the preference field in MX records, and is intended to prevent mail looping. If the mailer is on a host which is listed as an MX for the destination host, the mailer may only deliver to an MX which has a lower preference count than its own host.