Yup, Screamer, they must all do this. My "N" happens to be my ex, and email happens to be the primary way we "communicate". His emails are defensive, raging and even his screen name is CAPITALIZED and yelling, just like him. I believe his new wife helps him construct his emails most of the time, so they don't actually even sound like him...ie: better vocabulary and more poison.
She cannot have children, mine don't care for her, so boy is she pissed (and married to a cheating bastard, too....poor girl).
Before I even open email, I have to breathe deeply, consiously set my intention to let go of any negativity I may pick up if I open my email and his name is there. I know it's bound to be nasty..even if it is just travel info, he infuses it with either "poor me" I "have" to go away....or "I DEMAND" language, or who the hell do you think you are for having an opinion, etc.... I really have to work at letting it go, it is a process, but if I don't do it, I carry his shit for days. (looking at it like that helps to let go...why would I willingly carry feces?).
Any way, yup, they are all about them! My best response has been (because our emails were admissable in court I do respond) is "recieved email."
With your mom, say "OH well" to yourself and skip happily out of the room and on with your day! (and vidualize her shit/energy flushing out of your body!)