Spam is the opposite of relevance. Spam is irrelevant and interuptive. Its why spam simply doesn't work as a marketing tactic. Spam is non targeted and simply sent out indiscriminately.
If we want our messages to reach our audience, they must be relevant. And not just a little bit relevant. If the message is only slightly relevant, its still probably spam. It must be highly relevant if its going to reach the audience and cause them to take an action.