Using Norton VPN for my iPhone blocks my emails on the cellphone

I cannot receive (send email responses) via my phone, though I use to be able to. I'm force to shut off VPN on iPhone and get email, then turn VPN on again. I have a iPhone 7 with the latest update 14.8.1

What you appear to be seeing is your email provider blocking access to your account from known VPN IP addresses. This is done to protect your account from unauthorised access. When you are using the VPN feature, your email provider sees that someone is trying to access your account from a location they are not expecting you to be using.  There is nothing Norton can do if this is what is happening. 

You might try contacting your email provider to see if there is a workaround for VPN use.