For what its worth, early career and in undergrad, I would worry about emailing too and probably spend too much time just being nervous about it. Then you get enough replies back from the big fish that are literally just

"ok

Sent from my iPhone."

And then you start feeling more comfortable. Then before you know it, you are pounding out an email in 30 seconds and tolerating the occasional typo or forgotten attachment. I realized all the anxiety I had over emailing was entirely self imposed, frankly its never that serious. You are human after all just like everyone else.