Enterprise SendMail mail Server creation (1)

Create | server | Email is the most commonly used mail server, and many enterprise users often use e-mail systems. In the system, is the most widely used e-mail server. This article will provide a more detailed description of how to build an e-mail server to meet the basic needs of the enterprise. Is the most important message transfer agent. It is important to understand the working mode of e-mail. In general, e-mail system can be divided into user agent, transport agent and delivery agent several parts. The user agent is used to accept the user's instructions, sending the user's letters to the letter transfer agent, such as. The delivery agent obtains the letter from the letter transfer agent to the end user's mailbox, for example. When a user tries to send an e-mail message, he cannot send the letter directly to the other's machine, and the user agent must try to find a letter transfer agent and submit the message to it. After the letter transfer agent gets the message, it first saves it in its own buffer queue, and then, depending on the destination address of the message, the letter transport agent finds the message transfer proxy that should be responsible for the destination address, and then transmits the message to it over the network. After the other's server receives the message, it stores the buffer locally until the recipient of the email is viewing its e-mail. Obviously, the message transfer is from the server to the server, and each user must have the space (called the mailbox) where the information is stored on the server to accept the message (the message is not sent by this restriction). As you can see, the primary job of a message transfer agent is to monitor the user agent's request, locate the corresponding mail server based on the destination address of the e-mail message, transfer the mail between the servers, and buffer or submit the received message to the final delivery program. There are many programs that can be used as message transfer agents. In the system, is one of the most widely used, it is a free software, can support thousands of or even more users, and occupies a very small amount of system resources. However, the configuration is very complex, so some other tools, such as, and so on, are also used. When the program gets a message to be sent, it needs to be determined by the destination address to deliver the letter to the corresponding server, which is implemented through the service. For example, the destination address of a message is, then, the format, then, through the query to determine the need to send a letter to a server. In the data, the email is related to the exchange of letters (,) records, for example, in the apparent, at the server, and then try to send the message to either of them. In general, the priority level of the server in front is higher, so the server tries to connect to the port, trying to forward the message to it. If successful, the server's task is complete. After this task, it will come to an end. In general, the server automatically forwards the contents of the letter to the target host. However, there are cases where the target host (for example) may not exist, or do not perform the service, but rather by its server to perform the management of the letter, the final letter will be saved on the machine until the user is able to view it. RecordUsually because the other person does not have a mail exchange host, you will attempt to chat directly with the host from the mail address and send the message. For example, the record, so that after the server fails, will attempt to send the message from the address and directly to the other conversation.