Google should provide the option of automatically encrypting your incoming email with your public PGP key, if you provide one. They could similarly automatically encrypt your Sent folder (not the actual sent messages). That way, even if your account is compromised, or emails subpoenaed, they can't read the emails without your private key.

That's exactly what I do on my system anyway. I host my own email as well though: https://grepular.com/Automatically_Encrypting_all_Incoming_E...