So do emails themselves. It's in the name: it's "electronic mail". The underlying implementation has modified its behavior to fit the physical properties of how letters usually work to some degree. You think an email is something different than a text message, or a Slack message, or even a website or a video, when it is information that reached you by electrons moving a certain way in a wire. Or multiple wires. Or electromagnetic fields in space. Or photons in strands of glas or plastic.

It's all abstract, it's all metaphors.