Is there a way to send mail to someone who isn't your friend?

[Vahlnir]

That would be a terrible feature, and we'd all be spammed with botmail constantly.

Which would be arguably worse in some respects than things were at one point with RMT. They were spamming me with tells at least 2-3 times a minute before SE made them easily reportable. There were very few people who hadn't set themselves in busy status to avoid it. We don't need them opening another door for spam, because they totally would use it.