Is there an official rule on whether it’s die E-Mail or das E-Mail? I’ve heard people use both, although more commonly the female form.
According to the Duden, both feminine and neuter genders are possible. My personal experience is that indeed most people use die E-Mail in Germany; according to the comments, people tend to say das E-Mail in Austria and Switzerland. Note that the Duden lists the word as E-Mail, not Email (the latter being also a German word for enamel).