Frequency and relevance go hand in hand. Only talk to individuals in your audience when you have something to say. The idea that -it’s Thursday and I’ve got to blast my email- is seriously outdated.
Marketers have few opportunities to engage their customers and prospects. You can’t afford to waste that touch, so don’t. If you don’t have something to say, don’t say it.
A Japanese interesting saying sums it all up : “Before you open your mouth, make sure that the sound that you are going to make means more than silence”.
So what happens if you email a lot, but with no relevancy? In the long run, your audience will ignore you. Because your audience pays no attention to irrelevant email, they miss the ones that might actually have some value. The result is that you both miss out on an opportunity.