E-mail Architecture and Services
The message security service is hosted, actual detection and filtering of suspicious mail occurs not in your email environment, but at our external data center. This is a robust and secure cluster of servers that sits between your users and the Internet, and is wholly managed by our personnel.
To set up service for users, you need only register your mail servers, domains, and users with the service. Then you configure their filtering and services. You can do this all from a standard Web browser, without having to install or maintain any separate hardware or software.
Once service is set up, all incoming traffic to users is filtered at the data center according to your configuration—before it reaches your server. Within milliseconds, heuristics-based anti-spam and virus engines separate spam and viruses from legitimate messages. Legitimate messages are delivered to users without delay, while suspicious mail is either deleted or diverted to a Quarantine where you or your users can review it.
Service architecture (1) Users’ email arrives from the Internet as usual, and is filtered at the data center, before reaching your server. (2) Legitimate messages are delivered to users without delay. (3) Spam and viruses are diverted to a Quarantine.
Note: he data center accepts incoming email in SMTP format on port 25.
They normally consist of two subsystems: the user agents, which allow people to read and send e-mail, and the message transfer agents, which move the messages from the source to the destination. The user agents are local programs that provide a command-based, menu-based, or graphical method for interacting with the e-mail system. The message transfer agents are typically system daemons, that is, processes that run in the background. Their job is to move e-mail through the system.
Typically, e-mail systems support five basic functions. Let us take a look at them.
Composition refers to the process of creating messages and answers. Although any text editor can be used for the body of the message, the system itself can provide assistance with addressing and the numerous header fields attached to each message. For example, when answering a message, the e-mail system can extract the originator’s address from the incoming e-mail and automatically insert it into the proper place in the reply.
Transfer refers to moving messages from the originator to the recipient. In large part, this requires establishing a connection to the destination or some intermediate machine, outputting the message, and releasing the connection. The e-mail system should do this automatically, without bothering the user.
Reporting has to do with telling the originator what happened to the message. Was it delivered? Was it rejected? Was it lost? Numerous applications exist in which confirmation of delivery is important and may even have legal significance (”Well, Your Honor, my e-mail system is not very reliable, so I guess the electronic subpoena just got lost somewhere”).
Displaying incoming messages is needed so people can read their e-mail. Sometimes conversion is required or a special viewer must be invoked, for example, if the message is a PostScript file or digitized voice. Simple conversions and formatting are sometimes attempted as well.
Disposition is the final step and concerns what the recipient does with the message after receiving it. Possibilities include throwing it away before reading, throwing it away after reading, saving it, and so on. It should also be possible to retrieve and reread saved messages, forward them, or process them in other ways.