In Search of... A definition for e-mail spam

According to Wikipedia, e-mail spam is defined as follows:

"E-mail spam, also known as unsolicited bulk Email (UBE) or unsolicited commercial email (UCE), is the practice of sending unwanted e-mail messages, frequently with commercial content, in large quantities to an indiscriminate set of recipients. (http://en.wikipedia.org/wiki/Spam_(electronic)#E-mail_spam)"

This definition is okay, but is overly broad. I would like to propose the "Triangle of Spam" in an effort to more accurately define the problem.

Simply put, for any piece of e-mail to be considered "spam" it must be unsolicited, anonymous, and high volume. If any one (or more) of these characteristics is not met, the e-mail can be considered unwanted, but is not "spam."

It is important to distinguish between "spam" and simply unwanted e-mail. For example, are "Lowest Fare" updates from United Airlines spam or, in my case, simply unwanted (I never fly United)? While I'm sure I did fly United at some point in the distant past, I certainly do not plan on flying United anytime soon. Technically speaking, United has the right, by virtue of our "previous business relationship," to send me these updates. However, in my particular case, these are absolutely unwanted e-mails, but they cannot (or should not) be considered spam.

I am very interested to hear what other people think of the "Triangle of Spam."