Tbh whatever LLM of your choice is great to get through that for me. Just plop in the mail and what you want to respond, and then take the output and edit so it matches your personal style. It really has helped me to get through that anxiety. And I don't feel like it's less me, it's what I want to say, and I edit it to make it personal.
I mean "Hsssssssss Grrrrrrr tsk tsk tsk Eeeeeee! Chh! Chh! Ch-ch-ch-ch."