The salesperson's email was targeted to me directly. Clearly, someone had done enough research to know I am a speaker, and that I might benefit from their product. The product was fine, and a lot of speakers will find it valuable. It is not valuable to me right now because I have something that does what this product does in a way that I like better.
Out of courtesy, I explained that I was not interested at this time, as I am satisfied with what I am using. (I hope this rings a familiar bell for you.)
The salesperson sent a note suggesting that his product is better than what I am using, and it very well may be, but I am still not moving.
A few days later, the salesperson sent me an email to tell me that I was either uninterested or too busy, so if he didn't hear from me, he would remove me from his contact list.
Ultimately, you have no power
When you are pursuing a prospective client, you don't have the power to issue an ultimatum. You can't say, "If I don't hear from you, I will remove you from my contact list." You will have many prospects who accept your offer.