Unable to change email on iPhone 6s

I recently upgraded to iPhone Xr & gave my 6s to my husband. I did not erase the phone, just signed out of it & signed my husband on with his apple id. I switched the emails by going to "add new account" in the passwords & accounts settings, but my email still comes up on the mail app, instead of his. If I try to add him as a new account again, it says he has already been added. How can I get my email account to delete and his to appear? What else can I do?