I think it would be useful to have the latest email (or any email that you sent in the past) available somewhere on the website as well.

If it wasn't for your comment here, I wouldn't be able to see an example.

On a more personal note about the email, I'd drop the first paragraph, or make it shorter and focus on what you promised to send.

One great daily mail that I've subscribed and really enjoy to read is from the daily stoic [0]. They are quite short and to the point everytime.

[0] - https://dailystoic.com