It's something in the sender's email
I'm not sure if it's Blackberry emails, or windows - but I've had the experience too of typing a long time horizontally. When the message is received, it looks normal (as it does when I check my sent folder). I figure it's something in the sender's email that doesn't set the format in a way compatible with a mobile device. Most of the time, my emails wrap in the expected way. It's only when I respond to some emails. I'll start to note when it happens.