Everyone once in awhile an email account will dissapear on your iphone 6. Don’t worry your not the only one this is happening or has happened too. sometimes in the settings it will show but going into the mail app your email wont appear. First thing you want to do is try and reboot your iphone 6. If that doesn’t work delete the account, and after restarting you phone and re add the email. Disappearing email accounts on your iphone 6 sometimes has to do with a specific email provider, so if you find an email account not working correctly on your iphone 6 just add another one since most people have more then one email account.