It really depends on your threat model, what you are using email for and the information you are passing through it. As others have said, email is not private but unless you are some political dissident, criminal or just want to go down the privacy rabbit hole then something like hosting your own email or using a service like posteo, proton or tutanota is good enough.
Keep in mind, while you can lock down your phone to the highest degree, we still live in a surveillance economy / state. Use a credit card? It's being tracked and the data sold. Walk on the street? You're likely on a surveillance camera, or some tourist might inadvertently include you in a photo they are taking, then upload it to social media where subsequently your face might be analyzed and possibly tied to your identity (heck even friends and family do likely do this and actually tag you in the photo making it all the easier). Unfortunately, even with the most locked down phone and computer operating system on the planet, big tech still has something on you.