Here I go again: back to rule #1 - write for your readers.
An interesting chart came along in the email today from Marketing Sherpa. It's the results of benchmark survey.
Highlight: the biggest reason (cited by 58% of respondents) why they stopped reading or unsubscribed from email newsletters was that they were not relevant to them.
Add to that the 20% who said "it doesn't reply to me" (not sure what the difference between the two answers, but anyway...) and you get more than three fourths who cited relevance as their main concern.
Makes you think.
Putting your reader first is rule #1.