[threeseed]

Email is not a social network.

It is equivalent to a text message or phone call.

[DeepYogurt]

You might call it a network of social connections.

[TeMPOraL]

Also, people call e.g. Snapchat a social network. But by this definition, e-mail is much more of a social network than Snapchat.

[DeepYogurt]

I guess that gets at the point that the term social network is poorly defined.