[LinuxBender]

In addition to what others have already said, one can back up their emails and archive them wherever. This is useful not only for account termination but also for migrating to other email providers. Combine this with using a custom domain and one can have much more control over their communications. One can choose whether to leave emails on the server or move them locally and manage backing them up locally or even push an encrypted backup into the cloud.

Thunderbird can encrypt emails very easily to at least keep the body of the email hidden from machine learning. There are how-to's and videos for creating and managing encryption keys.