论文代写-Postfix邮件传输。Postfix通常采取一些措施来避免信息的丢失。在收到确认之前，Postfix调用flush和fsync将所有数据保存到磁盘。并检查所有系统返回的结果，以避免错误。大多数人会选择Sendmail作为邮件服务器，而Sendmail确实是一个很好的MTA (Anderson & Johnston, 2002)。然而，Eric Allman的设计考虑主要是邮件传输的成功与否。不幸的是，网络环境安全问题可能会遇到发送邮件。在大多数系统中，Sendmail只能作为根用户运行，这意味着任何漏洞都可能导致非常严重的后果。此外，Sendmail无法承担高负载操作。
Before comparing different MTA’s, the designing criteria of MTA’s should be discussed. Regarding to MTA’s function and purpose, the safety of the information carried by the email should be the most important to consider. The usability and the efficiency of transmission of the MTA also matters to its users. Design goals, worries about safety, the beginner or expert level user concerns and more also play a strong role when it comes to the development of the MTA.
Postfix is based on semi resident architecture interoperability process and each process complete specific tasks without any specific process derived relationship (parent-child relationship). Moreover, a separate process perform different functions has better isolation compared to single block program. In addition, this implementation method has some advantages. For example, each service such as address rewriting can be used by any Postfix components without process creation overhead, only need to override a postfix address.
The design goal of Postfix is to be a replacement for Sendmail. For this reason, many parts of the Postfix system, such as local delivery procedures can be replaced easily by editing the configuration file like inetd. This makes Postfix and Sendmail to be better compatible, and for users of Sendmail, the transition to Postfix would be easier.
The core of Postfix is realized by more than 10 semi resident programs. Postfix communicates between these processes through the UNIX socket or protected directory under the FIFO to ensure confidentiality.
The amount of data transfer between Postfix processes is limited. In many cases, only queue file name and the list of recipients or some state information in the process of data exchange between Postfix information. Once a message is stored in the file, in which it will be saved to a mail delivery program.
Postfix usually adopts some measures to avoid the loss of information. Before the receipt of confirmation, Postfix calls flush and fsync to save all data to disk. And checking all the system returned results to avoid error.
Most people will choose Sendmail as mail server, and indeed Sendmail is a good MTA (Anderson & Johnston, 2002). Unfortunately, Internet environmental safety problem may encounter to Sendmail. In most systems, Sendmail can only be run as root, which means that any vulnerability may lead to very serious consequences. In addition, the Sendmail cannot afford high load operation.