What is Email and How Does It Fit in the Bigger Picture?

A Taxonomy of Interpersonal Communications

nsb@mimecast.com, August 5, 2011

Many discussions about the future of email suffer from a muddled understanding of its past and present. Towards the goal of elevating and clarifying such discussions, what follows is an attempt to place email in a more accurate perspective.

People communicate in a variety of ways, but they are largely characterized by their posiiton along three dimensions: Temporal, Media, and Community.

The Temporal dimension characterizes the timeliness of the communications. At one extreme, speech and "instant" messages are in fact nearly instant (though technically bounded by the speed of sound and light, respectively). They are delivered quickly enough to create what is perceived as a real-time conversation. Towards the other extreme. postal mail is delivered over days or weeks, creating a highly asynchronous user experience. (At a further extreme, consider a message in a bottle, or NASA's attempts at interstellar communication using SETI and the Pioneer spacecraft.)

The Media dimension characterizes the types of information that can be conveyed, such as speech, sound, pictures, moving images, text, and much more. (Over 1300 such media types, also known as MIME types, have been registered as of 2011.)

The Community dimension characterizes the set of people who can communicate with each other and the symmetry or reciprocity of that communication. This can range from the people in a single room for normal conversation (or a single bed for pillow talk) to everyone on the Internet, and ultimately will be extended to every person in the world, and potentially every sentient being in the universe. The Community dimension also characterizes imbalances in communication capabilities, such as read-only news feeds or mailing lists. (The idea of who can communicate refers in this context to the usual intended or inherent characteristics of the medium. One should always bear in mind that a determined government or other opponent can eavesdrop on nearly anything. Some form of code or encryption is appropriate for all of these technologies when privacy is essential.)

These three dimension allow us to categorize the differences among communication technologies, and to more meaningfully address such as questions as "is email dying?" or "what's really new about social networks?" The following table compares some basic communication techniques:

Communication Technique Temporal Characteristics Media Support Community Structure

Face to Face "Instant" Spoken languages, sign languages, body language, facial expressions, bodily odors Open to everyone close enough to hear, see, or smell

Postal Mail Days or Weeks Written languages, images, small objects Generally private between sender and receiver

Telegraph or Telex Hours or Days Written language in highly restricted alphabets, often highly length-constrained Supposedly private between sender and receiver, but inevitably seen by multiple intermediaries in transit
Fax Seconds to Hours Written languages, blurry images Muddled: theoretically sender-receiver private, but often seen by others, and often hard to reply to

Instant messages Seconds Written language, often abbreviated, often highly length-constrained Mostly private between sender and receiver

Email Seconds to Hours All known media types, but primarily written language Mostly private between sender and receiver(s), but ease of forwarding creates surprise exceptions. In modern email, the community of potential correspondents is everyone on the Internet, but earlier versions of email were closed to much smaller communities, and some modern social network systems appear to be pushing email back towards such "closed gardens."

Email Lists Seconds to Days All known media types, but primarily written language Confusing; community membership is often opaque, read/write permissions are often asymmetrical, ease of forwarding creates surprise exceptions

RSS Feeds Seconds to Days Primarily text, but can contain (and often links to) any media type. Similar to Email Lists, but less confusing because the asymmetries are clearer so attempts to make unpermitted replies are less likely.

Printed publications Months to Years Primarily text, but often including images Generally everyone who can find a physical copy and has money to buy it or can find it in a library. Replies are possible only through postal mail and generally only with substantial difficulty

Web publication Seconds to Centuries All media types Generally open to the world, but authentication sometimes required. Reciprocal communication can be very easy or very hard depending on the web site

Message in a Bottle Weeks to Eternity Whatever fits in a bottle Creates ad hoc community of sender and finder only; extreme asymmetry and random delivery means the finder can't usually reply

Interstellar Communication Years to Eons Encoded radio waves, durable physical objects; encoding issues may render messages meaningless upon delivery Life spans of mortal beings likely preclude true conversation; participants might be more accurately characterized as the sending and receiving civilizations.
Social Network Seconds to Years Varies, but often all known media types Varies wildly, including private communications, public communications, ad hoc groups, lists of "friends" or "circles." However, social networks have also reintroduced the "closed garden" of earlier email systems, typically restricting communication to users of a single system.

The final row in this table begins to clarify why the rise of social networking systems has created substantial confusion. Social networks combine capabilities of a number of previous communication systems, causing some to wonder if those earlier systems have become obsolete. However, they are unlikely to become obsolete until the newer systems can match all their important characteristics. (And sheer inertia might allow them to survive longer still.)

Thus, for example, email, having evolved from a "walled garden" into near-universal coverage, isn't likely to go away as long as social networks lack its universal reach. You may prefer to send messages to your friends on Facebook rather than by email, but until you can reach nearly anyone that way, you're not likely to give up your email account.

The continued ubiquity of email is explained somewhat by the highlighted row. Email occupies a "sweet spot" of quick, media-rich, reciprocal, and universal conmmunication. Social networking technologies may match or better it in the future, but it won't be easy to match the combination of advantages that email has accrued over nearly fifty years of evolution, let alone the inertia of its entrenched position in the market.

Communication Technique	Temporal Characteristics	Media Support	Community Structure
Face to Face	"Instant"	Spoken languages, sign languages, body language, facial expressions, bodily odors	Open to everyone close enough to hear, see, or smell
Postal Mail	Days or Weeks	Written languages, images, small objects	Generally private between sender and receiver
Telegraph or Telex	Hours or Days	Written language in highly restricted alphabets, often highly length-constrained	Supposedly private between sender and receiver, but inevitably seen by multiple intermediaries in transit
Fax	Seconds to Hours	Written languages, blurry images	Muddled: theoretically sender-receiver private, but often seen by others, and often hard to reply to
Instant messages	Seconds	Written language, often abbreviated, often highly length-constrained	Mostly private between sender and receiver
Email	Seconds to Hours	All known media types, but primarily written language	Mostly private between sender and receiver(s), but ease of forwarding creates surprise exceptions. In modern email, the community of potential correspondents is everyone on the Internet, but earlier versions of email were closed to much smaller communities, and some modern social network systems appear to be pushing email back towards such "closed gardens."
Email Lists	Seconds to Days	All known media types, but primarily written language	Confusing; community membership is often opaque, read/write permissions are often asymmetrical, ease of forwarding creates surprise exceptions
RSS Feeds	Seconds to Days	Primarily text, but can contain (and often links to) any media type.	Similar to Email Lists, but less confusing because the asymmetries are clearer so attempts to make unpermitted replies are less likely.
Printed publications	Months to Years	Primarily text, but often including images	Generally everyone who can find a physical copy and has money to buy it or can find it in a library. Replies are possible only through postal mail and generally only with substantial difficulty
Web publication	Seconds to Centuries	All media types	Generally open to the world, but authentication sometimes required. Reciprocal communication can be very easy or very hard depending on the web site
Message in a Bottle	Weeks to Eternity	Whatever fits in a bottle	Creates ad hoc community of sender and finder only; extreme asymmetry and random delivery means the finder can't usually reply
Interstellar Communication	Years to Eons	Encoded radio waves, durable physical objects; encoding issues may render messages meaningless upon delivery	Life spans of mortal beings likely preclude true conversation; participants might be more accurately characterized as the sending and receiving civilizations.
Social Network	Seconds to Years	Varies, but often all known media types	Varies wildly, including private communications, public communications, ad hoc groups, lists of "friends" or "circles." However, social networks have also reintroduced the "closed garden" of earlier email systems, typically restricting communication to users of a single system.