Book Review: The Book of IMAP

IMAP is one of the most common protocols for e-mail servers on the Internet. Web-based e-mail services like Gmail and Hotmail use IMAP to retrieve and display e-mails in the browser, and e-mail clients like Microsoft Outlook or Mozilla Thunderbird support the protocol. In The Book of IMAP, there is a thorough practical explanation for setting up e-mail servers with courier IMAP or cyrus IMAP. By default, these include the POP3 server. IMAP is a more mature version of POP3 allowing users to manipulate operations on their mailboxes stored on the mail server. 

The book is divided into three main parts - the first deals with the generic set up and maintenance of IMAP servers, Courier-IMAP and Cyrus-IMAP implementations are covered in the second and third parts. 

For large scale implementations of IMAP mail servers, there is a requirement to efficiently handle the mail requests in real-time. For this purpose, there is the requirement of load-balancing among servers connected to a common storage at the backend via SAN/NAS. An alternative way is to split the mail database access across several servers based on some ordering of the mail accounts. Both of these implementations are explained in detail. Again, for very large environments there is the possibility to have a IMAP proxy arrangement in place which can each lead to  the load balancing arrangement of IMAP servers connected to the fast storage backend.

Other important topics covered include setting up webmail clients for these mail servers such as Squirrelmail and Horde/IMP, migration of IMAP servers due to reasons such as new IMAP server software or migration from POP3, in-depth discussion for the cyrus and courier IMAP mailserver configurations and features.

To summarize, the book is a useful and thoroughly technical read for the mailserver administrator working on IMAP or related professionals wanting to know more about this opensource mailserver technology.