Possible language settings in your email client? Does any character other
than @ appear instead? What country are you in? It appears in different
places depending on nationality. On mine (UK) it's Shift-apostrophe. In
some countries this will give you a quotation (") symbol instead. Try
Shift-2 instead. If this works then your email client is probably set for
the wrong language/keyboard.
....Unless of course you're using Windows Mail for both email and news, in
which case I don't know, as it's obviously working in this thread.
I've just noticed your post was written in Unicode (UTF-8). It actually
appears in the title bar of this reply, and that's the first time I've seen
it. This may have a bearing on the subject. Unfortunately I can't help
here. Hopefully someone else can guide you through setting the right
character set.