Here in the US, where it all started, we mostly say email for the message...and I'm pretty sure the hyphen is doomed as far as we are concerned, I certainly never write it, and haven't since about 1997, even though spellcheckers complained about it back then. Microsoft Word, the real authority on the spelling of English words, since they control via their spell-checker what spellings are allowed for about 80-90% of writers, considers both acceptable, and Google gives only 58,400,000 hits for "e-mail", verses 474,000,000 hits for "email", that's around eight times as many.
It's a natural progression for e-mail to loose its hyphen in English, as well...words like buttermilk often start out as adjectival noun + adjective, "butter milk", then gain the hyphen, "butter-milk", and finally loose it, to become the modern "buttermilk", or at least that's what I was taught in Elementary school. Some, like ice-cream, do get stuck half way.
E-Mail is a bit slow to write on a keyboard, but I definately prefer it in German to Email...one of the best things about German is that you can tell how to pronounce almost any word just by reading it...I believe Email would be the first German word which has a different meaning depending on how you pronounce it.