Great question, something that I have struggled with as well, and unfortunately I don’t have a perfect solution either.
I did try adding some personal info about be in there, such as “I’m X, a dad of 2, and lover of remote-controlled airplanes. Just wanted to let you know I’m a real person looking to help you solve Y as much as possible”.
I also tried adding in something like “This is not an automated email - I’m writing this from my personal computer at 5:31pm on Wednesday.”
Neither of those really had any effect, but what has helped is to not ask a question that can be answered with a simple no. Instead phrase your question to make them always have an answer. Example - instead of ‘Did you have any questions?’ try ‘What questions can I help answer?’
I think it’s also important to keep it short, like you have done.
What’s your response rate from the template you have been using above?