[chacham15]

> They're not entitled to the contents of the email because the service can operate without the contents.

This is mistaken. It is not the case that the service must operate by law. The service can only operate if it does not infringe civil liberties. To be more specific, it must not violate the fourth amendment of the constitution. The reason that metadata does not violate the fourth amendment is that there exists an expectation for whomever you give the message to to actually read the metadata much in the same way that you expect the post office to read the mailing address.

As I was trying to say in the parent comment, Lavabit, upon receipt of an email encrypts the entire email including the metadata. This still falls short of relieving the expectation I previously discussed because it still receives the email unencrypted. Hence, the government will argue that it has a right to the entire contents (even though the headers may suffice in some cases).