How is it secure if you are using shared hosting with a Bluehost owned SSL cert? Are you a crypto expert? What happens to "destroyed" emails? Are they deleted

How is it secure if you are using shared hosting with a Bluehost owned SSL cert? Are you a crypto expert? What happens to "destroyed" emails? Are they deleted from the "secure" database or are they just flagged as deleted? Data is valuable, and it's very tempting for individuals with zero oversight to archive data. In my opinion, there is more of a need for a secure SMS type service, but it's very hard to trust a random private company or individual.