If I ever receive an email from someone who signs at the bottom and I don't recognise the first name (i.e. it's foreign), I would never assume the gender of that person. I would just right back: Dear or Dear .
But people are always writing back to me 'Dear Mr '. I know it's not the biggest issue on the planet, but it's bloody irritating! If they're going to be presumptuous, why not assume I'm a woman, for goodness' sake?