[kenning]

Friend works in data law and says that it's ambiguous. One of the problems is that people use personal information in their email. Also, you have no idea if it's actually personal information or just a nickname they've given themselves. For these reasons it looks unlikely that emails will be considered personally identifiable information.

[guitarbill]

That's unlikely to be true. And people are stupid, and will use their email address - just look at e.g. the Ashley Madison hack. So for most people, it's personal information, and the law will probably treat it as such.