[MacsHeadroom]

In most cases receipt of an e-mailed subpoena could be shown to have been opened by looking at a mail provider's logs (ex Gmail). It's likely that a core developer for the Tor Project does not receive email in such a way, meaning receipt could be trivialy denied.

But this is all beside the point, because an NSL could never be sent to anyone over internet postcard. Clinton discussed national secrets over email and look what happened to her.