Since SMTP transfers things unencrypted, you kind of have to assume that a bad actor with reach as wide as the NSA's is intercepting all your email regardless of who your provider is. There's really no solution there, since the company from which you order your suppositories isn't using end-to-end encryption to send you their order confirmations.

That said, I still 100% support getting off of the free email providers in order to wave a middle finger at surveillance capitalism.