Mark Crispin, father of IMAP, RIP

Mark Crispin, father of the Internet Message Access Protocol (IMAP) died on December 28, 2012. Due to the contribution Crispin made to email interoperability and access, his passing deserves the acknowledgement of the global email community.

Although it’s now regarded to be an outdated protocol because it does not support the advanced features of modern email systems, IMAP still has a dedicated band of followers and is used by tens of millions of people daily to fetch email from Gmail, Exchange, Zimbra, and just about every other email server on the face of the planet. The major value of IMAP is its sheer ubiquity, with the golden rule being that if a client can’t access a server using another method, it probably can using IMAP.

The world of email was very different when the first versions of IMAP were written at Stanford University in the mid-1980s. The vast majority of mailboxes were served by proprietary systems such as Digital’s ALL-IN-1 or IBM PROFS and the Internet was a loose collection of servers connected with dial-up telephone links. The Post Office Protocol (POP) existed then as it still lingers on today, but only allowed users to download messages from a server. This sufficed in many situations then – servers and clients alike were resource poor and it was deemed to be a good thing to remove items from server mailboxes to bring them down to clients for processing.

Crispin conceived IMAP as a mail access protocol that advanced the state of the art by allowing access to more than an Inbox folder on the server, supported concurrent access to mailboxes, and offered much more functionality to manipulate messages than the POP protocol allowed. Originally developed in Lisp, a language much favoured by people working on Artificial Intelligence at the time, on a Digital TOPS-20 computer, the value of IMAP was realized in its fast evolution and adoption to the point where IMAP4 appeared in 1994.

IMAP4 has been extended many times with additions by vendors (for example, Microsoft extends IMAP4 to allow delegate access to Exchange mailboxes) and industry groups (the P-IMAP effort to create push email notifications to mobile devices in 2006 is a good example of an effort to extend IMAP to deal with the demands of modern messaging). Work to extend and refine IMAP4 persists today, with IMAP4 Rev 1 (RFC3501) usually regarded as the basic standard.

It’s hard to think of many individuals in the field of email whose work has had such an influence as Mark Crispin. May he rest in peace.

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Tony Redmond is a senior contributing editor for Windows IT Pro and the author of Microsoft Exchange Server 2010 Inside Out (Microsoft Press) and Microsoft Exchange Server 2013 Inside Out: Mailbox...
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