[ithkuil]

if emailed, what prevents you from leaking it (along with other recent content of your email inbox) claiming somebody hacked your email ?

[MacsHeadroom]

More importantly, what prevents half a dozen email servers from leaking it all over the place?

The notion that an NSL would be sent over internet postcard is laughable, whether or not it's true.

[modoc]

Fear of prison?

[maze-le]

You can get into prison because someone hacked your email account?

[modoc]

If they dig into it and decide that you did it yourself, as the parent suggested, then yes, you would have a serious risk of prison time for willfully violating the NSL.

[PeterisP]

Did someone hack your email account?

You would expect such a claims to be severely scrutinied (including seizing all involved hardware for forensic analysis), and if you'd be making a false claim while having disseminated the information yourself, that would be a crime by itself in this scenario.