Based on the Pen Letter laws. Anything stored with a third party can be subpoena by the government. The reasoning is if one wanted to keep it a secret they woul

Based on the Pen Letter laws. Anything stored with a third party can be subpoena by the government. The reasoning is if one wanted to keep it a secret they wouldn't be sharing with a third party. If you use an ISP for email the ISP can be subpoenaed with you being aware. If you want run your own mail server from your house. A search warrant of your house for the mail server is required. Different notification standards.