With the increasing spread of e-mails, the security of e-mail system proves to be a paramount part of the whole online security network. An insecure mail server is vulnerable to attacks, such as junk mails, intrusion to the mail relay and the denial of service. In light of these facts, this essay introduces compares and analyzes the functions and operations of major mail servers. With detailed description of respective advantages and disadvantages, it also discusses the characteristics and related configuration issues of Postfix, one of the most popular and cost-effective mail servers. In general, Postfix has experienced escalating popularity, due to its efficient e-mail system and high security performance. However, although it has anti-spam functions, it still needs professional software support to deal with the increasing number of spams in the current online community.
The other MTA actually includes a specific version of the inetd to monitor the load average of MTA, but Qmail designed the internal mechanism to limit the system load and qmail-smtpd can safely run the INET. Qmail has limited technical support.
Qmail also has some other shortcomings. If it is not fully complied with the standard, it does not support DSN, but Qmail VERP can do the same work. Another problem is that the Qmail does not comply with the 7bit standard system and each time sends 8bit. If the mail receiving party cannot deal with this situation, the message will appear garbled.
it is easy to find that each MTA has its own strong features; none of them can cover all three criteria with high score. However in general, the Postfix is more usable than the other two. However, security for a MTA should be the most important feature, and all the other properties are built on this basis. Thus postfix can be seen as the best MTA among three MTA’s in general aspects. Usability is an important characteristic and in terms of usability as presented in chapter 3 already it is noted that Postfix was primarily a replacement for Sendmail and in thus being it will be able to support a set of users who are already making use of Sendmail. Thus, usability criteria rating for Postfix automatically goes up. However, an argument can be made that the comparison will not be complete until a more detailed comparison that looks beyond basic argument of usability, security and efficiency is done.