InformationWeek
Defining The Business Value Of Technology
October 12, 1998
Net Mail Scales Up
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By Dan Backman and Jeff Angus
he cost of deploying and maintaining traditional messaging systems escalates in proportion to the parade of power features publishers pack into every new version. The results are as frightening and bloated as Rush Limbaugh in a Spandex body stocking. But for emerging enterprises or for big, established organizations that have yet to standardize on a single messaging solution, there's an alternative: Internet Messaging Access Protocol-standard messaging. In the past, the alternative was thin-client Internet mail such as Post Office Protocol-standard offerings that would remove most of the training and maintenance burden in exchange for losing most of the features.
In the grand scheme of electronic messaging, IMAP lies halfway between a full-fledged groupware product such as Lotus Development Corp.'s Notes, Microsoft's Exchange, or Novell's GroupWise on one side and the simple interface of a POP, mainframe, or Unix-based mail reader on the other. In conjunction with the Simple Mail Transfer Protocol, IMAP has all the features necessary to provide client-server Internet E-mail capabilities to virtually any desktop client and back-end server. And while the feature set is in the middle, the administrative and maintenance burden is far lower than full-fledged groupware messaging systems.
IMAP clients have a significant advantage over POP. Where POP clients allow users only to download E-mail from a remote mail server to their desktop clients, IMAP clients add the ability to remotely access and manipulate messages on the server. Designed to help users who need the rich features of a graphical user interface-based desktop mail client and who must store and manage E-mail on the server, IMAP includes many features POP can't support. Dial-up users can download message components separately, allowing them, for example, to read the main body of a message without downloading a multimegabyte attachment.
Additionally, roaming IMAP-client users can store important messages on the mail server instead of worrying about finding a place to which they can download messages. IMAP also adds the advantages of server-side features such as shared folders and concurrent operations on a single mailbox; POP3 programs allow only one user and one concurrent session per mailbox.
While many Internet mail users still rely on POP, support for IMAP among Internet mail clients and servers is nearly universal. Any up-to-date Internet mail server or client should support both POP3 and IMAP4 for mail access, as well as SMTP for mail transport. The current versions of full-fledged groupware mail servers from Lotus, Novell, and Microsoft all support IMAP standards.
Many Incarnations Of IMAP
If you're in the market for an IMAP server, chances are your needs are focused in one of three areas. In the simplest case, an organization without concerns for legacy messaging systems might opt for a standalone Internet mail-server suite. However, if your organization already supports Internet mail on a legacy system but needs IMAP support (for instance, on a Unix server running Sendmail and a POP3 daemon), a standalone IMAP daemon might serve your needs. Finally, sites running proprietary or LAN-based mail systems, such as Novell GroupWise, Lotus cc:Mail or Notes, and Microsoft Exchange, might find that IMAP support is already available or can be added through a server-side plug-in or some other add-on product.
The first step in implementing an IMAP-standard product is to decide whether your IMAP server needs a fully functional SMTP message transfer agent (MTA), or whether you need an IMAP gateway on your existing mail server. If you're planning to support large mailing lists or need to deliver large numbers of outgoing messages, a multithreaded MTA will increase performance dramatically when transferring bulk messages.
A word of caution: Sites migrating from POP to IMAP services should examine some critical issues in terms of server scalability. Though POP is extremely server-friendly, IMAP places additional demands on the mail server. With IMAP, the mail server is no longer a simple mail drop, accepting incoming messages and storing them until they are downloaded by the client; under IMAP standards, the mail server must support users' short-term mail archives.
continued...page 2, 3
Read sidebar stories, "IMAP Searches For Its Place" and "An On-The-Road Protocol."
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