They are(were) a fully-encrypted email provider that had no ability to monitor your emails. Edward Snowden hosted his account there, and they had to shut down because of (probably) US government intervention.
"Either you are with us, or you are with the terrorists." - George W. Bush, Sept 20 2001
if you email a gmail account, or a gmail account emails you, obviously a copy will end up on both, at least temporarily.
I don't see what more they could do, as a provider - all your metadata and emails encrypted properly for you, shut down completely when (the NSA?) comes knocking.