Outside of the term "army for trump" I can't find any verbage like it used in the suspected email. I'm by no means a Trump supporter, but before I start slinging this email around at people I'd like to know it's absolutely authentic, and so far it's been shared by one person on Twitter, and a single random website made an article about said Twitter post. I can't really find anything else on it.
I'd like to be able to use this email as yet more proof of how obvious he is radicalizing his followers, but without more substantial evidence than a single Twitter post I fear I am doing exactly what his followers do by grabbing onto something fake and touting it as fact