Advantages of Qmail

QmailThere are many advantages. Please refer to the following section.

Practice has proved that Windows NT-based Exchange Server is not the best choice for enterprise-level email systems. Because of the high requirements on stability and other performance, large email systems generally use UNIX as the server operating system, for example, Hotmail uses FreeBSD and Solaris, BSD series is also used for domestic sites such as 163. Large enterprises that are pursuing stability can adopt FreeBSD and Solaris, while general small and medium enterprises can adopt Linux.

The traditional email system in UNIX systems has some defects in its system structure due to the limited number of users allowed by the design, making it difficult to withstand the access of a large number of users. For example, the widely used Sendmail system has the following limitations:

* Because the user information is stored in the/etc/passwd file, the authentication efficiency will be greatly reduced when the number of users is large;

* Emails are usually stored in the/var/mail directory. Each person's email is a file. If there are many users, there will be more mail files. In UNIX systems, when the number of files in a directory at the same level exceeds a certain number, the efficiency of the file system will be greatly reduced. When NFS is used to share a bucket, a serious problem occurs-due to the lack of File Locking Mechanism in NFS, when the traditional user mail storage format Mailbox is used, because all emails are saved in the same file, the email operation must be locked to ensure that there is no access conflict, which makes it not suitable for NFS storage;

* Because each user has multiple emails in the same file, if a network exception occurs during the user's email retrieval process, it is easy to cause a deadlock in the mailbox.

The preceding problems greatly limit the application of the Sendmail mail system when the number of users is large. In addition, users who use system users as email systems also have serious security risks. Therefore, to meet the needs of large capacity, you must improve the mail system architecture, especially the mail storage and user authentication methods, it can maintain good performance in the case of a large number of users.

Qmail is a new generation UNIX Mail system that can completely replace Sendmail-binmail system. It is also an Internet Mail Transmission Organization (MTA) based on UNIX operating systems ). It uses the standard Simple Mail Transfer Protocol (SMTP) To exchange information with other MTA instances on the Internet. To solve the mail storage problem of users, Qmail proposes the Maildir storage method. Each mail is saved as a separate file in the user's personal mail directory, which avoids locking. At the same time, Qmail supports Virtual domains and Virtual users, so that users in the mail system are independent of users in the UNIX system. Compared with Sendmail, Qmail has the following advantages:

* Security ---- Qmail divides the E-mail processing process into multiple sub-processes, and tries to avoid running as Root users. In addition, Qmail prohibits direct sending to privileged users (such as Root and Deamon.

* Reliable ---- direct delivery of Qmail ensures that E-mail will not be lost during delivery. Qmail also supports a new and more reliable mailbox format, Maildir, to ensure that the entire mailbox is not damaged when the system suddenly crashes.

* Efficient ---- running on Pentium BSD, Qmail can easily deliver 0.2 million emails every day.

* Simple ---- Qmail is much smaller than other Internet Mail systems. It implements Forwarding, Alias, and Maillist functions through a unified forward mechanism. Qmail uses simple and efficient queues to process delivery. Qmail-SMTPD can be started by Inetd, saving some resources.

Currently, the most popular free email systems in China, such as 163 and 371, are all developed by Netease. These systems use Qmail as the basic server software, NFS Network File System as the user's mail storage space, Maildir as the mail storage format, and provide multi-level directories to support a large number of users.

Compared with the free email system on the Internet, the email system users of large and medium-sized enterprises are mainly internal users. Although the number of users is less than 100,000 or, the user base is relatively fixed, however, the requirements for system security and stability are higher, and user management is more meticulous and cumbersome. If you can establish a complete user database in a unified Web form and provide email services and user management, it will greatly reduce the tedious work of the system administrator while facilitating users.

Qmail is a famous free software under GNU. Experts from all over the world have developed a large number of Qmail-based tools and patch software to further improve and expand its functions, vmailMgr (Virtual Mail ManaGeR) is one of them. It enhances the Qmail Virtual Domain function and provides a large number of commands to facilitate the establishment and management of mail system users independent of UNIX system users, provides rich management functions such as soft and hard space quotas. The virtual users of the mail server can also access their mailboxes through POP3 and IMAP standard protocols. It is particularly worth mentioning that VmailMgr also provides a set of CGI programs and PHP functions. With this set of programs, users can apply for a mailbox and change their passwords on the Web page, the email administrator can also easily complete user management and email system configuration on the Web page.

An excellent large enterprise email system should have the following features:

1. provides large-scale, high-speed, secure, and reliable email services for internal enterprise users, with thousands to tens of thousands of users.

2. The mail system supports various standard E-mail protocols and provides POP3 and IMAP mail access methods.

3. Provides the WebMail function. You only need one browser to complete all mail operations.

4. Provide 20 MB or larger email storage space for each user.

5. provides users with functions such as Mailing List, mail forwarding, and alias.

6. Create a user database system to save personal information during user registration for convenient user management.

7. Provide daily browser-based management for routine maintenance personnel

Through the complete introduction of the article, we are sure you are all tempted. Please take action and download and install him!

• Qmail mail storage mode Courier
• Qmail mail management VmailMgr
• Qmail Installation
• Email Forwarding rules for parsing Qmail
• Learn more about Qmail's working principles and configuration files
• Qmail Introduction
• Qmail on the mail server in Linux