Concepts |
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© 1997 Digital Integration (NZ) Ltd
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Document Conventions | |
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Push vs. Pull Protocols | |
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Simple Mail Server | |
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Multi-POP | |
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Multi Domain | |
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Gateway/Router Server | |
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Multiple Site Mail Server | |
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Mail Server & Gateway/Router |
To understand how i-Mail transfers mail to and from each system it may be connected to, it is important to understand some of the terminology that will be used. The methods of setting up i-Mail each have a schematic diagram showing the processes involved in moving mail from one location to another.
Icons which are used in the schematic diagrams.
The process of pushing and pulling mail is the domain that i-Mail was designed for. Traditionally for a company to receive mail for multiple recipients it is required that one of two messaging systems is set up.
Pull Mail System
The first method is to have each user at your company set up with an individual account at your ISP. This scenario uses the pull protocols to retrieve mail and the push protocol to send mail. Each workstation then connects to the internet and downloads his/her mail. The connection can either be made via a modem at each workstation (1) or through a shared modem or internet connection (2). This method works all right for a very small number of users however the cost of maintaining and adding users to the system becomes very expensive. The major drawback of this system is that when a John wants to send mail to Sarah, he must write his message, wait for the connection to the internet to become active and pay for the on-line time. For Sarah to receive her mail she must manually connect to the internet and download new messages. For John to get a quick response is almost impossible as the same process must be used to return mail back.
Push Mail System
The second and more sensible, but costly, method of transferring mail is by maintaining a permanent link to the internet. This uses push for incoming mail to the mail server, from the server to the internet and from the workstation to the server. Pull is used from the server to the workstation. In this way a local mail server can be set up on site to receive messages destined for you company. Now, when John sends a message to Sarah it will be stored on the mail server until Sarah looks for new mail. Because the mail is stored locally on the mail server Sarah can set her mail program to poll, lets say, every 2 minutes without the hassle of connecting to the internet each time. If mail exists it is automatically downloaded to her PC and she is prompted that a new message has arrived. The response to this message goes through the same procedure. In the given scenario the users have a round trip time of approximately 5 minutes from sender to response. Not a bad system.
The drawback for this configuration is in the cost of the internet link. While no messages are transferring over the line you will still be paying for the luxury of having the link active. This ratio of cost vs. mail traffic becomes expensive unless you meet the demands of the link.
Push & Pull using i-Mail
Push/Pull
Utilising i-Mail it is now possible to get the best of both push and pull protocols. i-Mail works as a mail server which processes mail for local users directly without needing to connect to the internet. This uses push from the workstation to the server and pull from the server to the workstation. Outbound mail for the internet uses any popular dial on demand TCP/IP router to connect to the internet when outbound mail is pending and inbound internet mail is collected from a pull mechanism at timed intervals. The timed intervals can be set at, for example, every hour of the day or at specified times on specified days, i.e. every two hours from 8:00am to 4:00pm Monday to Friday. This method facilitates fast local mail and allows you to receive internet mail in a fashion tailored to suit your companies needs. As your internet mail requirements grow, so can your i-Mail system cater for usage.
i-Mail utilises a single mail box at your ISP, providing they can forward all mail from your registered domain into a single POP account.
As a simple mail server i-Mail can be configured to work as a local mail server, retaining message files from senders until receivers connect and collect their mail. By setting up an internet account i-Mail will sort out mail that is destined for external users and send the messages out to the internet. Inbound internet mail is received on a timed schedule and stored in each users individual mail store.
In some cases you may have multiple mail accounts at your ISP which require downloading of mail. This is achieved with Multi-POP. Mail can be downloaded from any number of internet POP accounts, from any number of POP servers. As shown in the illustration Multi-POP can be used to download company mail and distribute it to the appropriate users and also receive personal mail directly to the users mail account. This allows users to replicate their personal mail systems at their office mail system. It is particularly useful for mobile computer users.
i-Mial can be configured to host multiple domains for a single company if required. This is uses Multi-POP to collect mail for each domain that you wish to host. Reasons for using Multi-Domain might be historical company names, multiple companies using the same network and e-mail system or simply multiple identities..
i-Mail has the capability of acting as an e-mail router for foreign e-mail systems. It is commonly used to provide a mechanism to retrieve mail from the internet for an existing messaging system that does not have dial on demand downloading capabilities. This includes such products as Exchange and GroupWise. These products provide support for SMTP mail which uses a push mechanism and require a full time link to be established with your ISP or to come to some agreement on what times you will be online.
By using the SMTP connector of the existing system, i-Mail will download messages from the internet, from a single POP mail account, sort the messages into their appropriate recipients and forward the messages on to the foreign mail system. The existing system will then take care of local message handling and outbound internet mail transfer.
The above image is a simple demonstration of how i-Mail can collect the inbound mail for another mail server on the network. It may also be installed on the same server as the existing mail system if it runs on NetWare. The example below demonstrates this functionality.
Using the remote domain feature of i-Mail, multiple sites may run linked, but separate, mail systems which can use a single internet connection. This is especially useful for companies that already have links set up between branches for file transfer. No matter how slow the link is between sites, i-Mail will transfer messages between the sites in the background ready for retrieval by local users.
The connection to the internet for multiple sites can be made either from each site, or in the case of high volume mail it can be more cost effective to maintain a single high speed link to the internet from a single point and have i-Mail forward messages to each downstream mail server.
In this slightly more advanced scenario we see i-Mail retrieving mail for a local GroupWise system, but also hosting two remote mail systems as well. This situation fits well when a parent company has smaller subsidiaries which may not be able to afford or do not require all of the enhanced features of the parent companies mail package. It also applies where the remote site connects but is separate from the main company.
The image shown demonstrates how i-Mail copes with keeping costs in the right place. Company2 may have a dedicated link or a dial-up link could be used and the cost be shared dependant on the direction of the mail. Company3 on the other hand must make the connection to Company for both incoming and outgoing mail thus wearing all transfer costs except for the internet mail. If the internet mail costs are to be paid for by Company3, they would have their own internet connection from i-Mail.
© 1997 Digital Integration (NZ) Ltd