Open source IMAP and POP3 server: Dovecot Configuration and usage

This article describes the open source IMAP and POP3 server--dovecot on the Linux/unix class system platform, and its solution for caching (caching) problems when NFS is stored as storage--dovecot Director. You will see how to configure Dovecot Director and how Dovecot Director works.

What & Why Dovecot

Dovecot This noun may be unfamiliar to many people, but if the mention of Courier,cyrus or UW, it must be a lot of people have heard. Yes, dovecot, like them, are IMAP servers.

Let's briefly introduce IMAP Server. Imap,internet Message Access Kyoto, formerly known as "Interactive mail http://www.aliyun.com/zixun/aggregation/34570.html" > Access Protocol, is used to access remote mail from local mail clients, such as Outlook,thunderbird, and so on. And more and more web mail, such as Gmail,hotmail, is now used to support IMAP.

Although Dovecot is an up-and-comer, but it is menacing, if you try to search the IMAP Server,dovecot in Google is ranked in the very front of the search results, from the side of the popular dovecot. But why Choose Dovecot?

1. High security. According to Dovecot's authors, security is highly regarded and emphasized from the design and implementation of Dovecot. Security here is not just about the traditional sense of security vulnerabilities, but also the reliability of software. The best corroboration of Dovecot's high security is the "reward". The Dovecot author, starting in 2006, rewarded GBP 1000 for the first person to be able to discover the "remotely exploitable security hole", with the result that 1000 pounds were still not available today. The "remotely exploitable security hole" here is not simply a software flaw. This shows that its security is very great. As a direct access to user data and mail applications, if there is an illegal access to the loopholes, the consequences of how serious.

2. High performance. The high performance here is not a generalization of how fast the Dovecot software itself runs, but specifically the high performance of Dovecot when accessing mailboxes. Dovecot is done by indexing standard mail storage formats mbox and Maildir. The index is transparent to the user, quietly in the background, and is incremental, which is done every time a new message or user modifies or deletes the message, thus minimizing the cost of indexing. Dovecot only index information that is frequently used by user clients, such as message headers, mail senders, and so on. Ensure that index files are not too large. In the mailbox when the number of messages is very small can not see the benefits of the index, but when the number of messages slowly increase, Dovecot shows his advantage: every time you open the mailbox, send and receive deleted messages are very fast. Compared to other traditional IMAP servers such as Uwimap, the index is not supported, so whenever you open a mailbox, you need to scan the entire file system, load all files, put into memory, the cost is conceivable. Another index is closely related to the topic we are going to discuss next.

3. Ease of management and scalability. Dovecot has a lot of plug-ins, making configuration very convenient and flexible. For example, for user authentication auth-mechanism, support PLAIN,CRAM-MD5 and so on. Here is an example:

For example, for user password Authentication passworddb, support password-file,ldap,sql,static and so on. The following is an example of SQL, very simple and intuitive:

Also, for example, to compute the disk quotas (quota) currently used by the user, Dovecot also provides plug-ins. There are a number of plug-ins like this, and the configuration is very simple, and the cost of learning and maintaining IMAP servers is reduced.