Late Night Emails...Rude?

Is there a "cut off time" after which it's as rude to send an email as it would be to call someone? Does one need to consider this when emailing an overseas colleague or client? I've seen how bright and loud that 'new message' indicator can seem in a pitch dark room

Or should people be responsible for their own notification preferences? One of the nice things about email communication is that it can be initiated at any time. Time zones are as nothing. Spontinaity reigns. That's surely a good thing.