I help companies with their digital strategies and have been a startup mentor.
Follow the sequence, WHY- HOW -WHO.

First discuss the problem and how it is becoming an issue. Also discuss some of the failed solutions which people have been using. Say that you will be sending a possible solution. This will make them curious while not being sales pitch.

Second mail should discuss the solution and how it can help address the issue. This will educate the customers.

Third mail will detail your solution and what exactly you do to implement the solution and solve the problem. Please add customer testimonials as well.

Hope this helps. Please feel free to call me if you wish to discuss further.
All the very best,
Sridhar