Is it possible to install the Android browser and email app if they weren't built-in?
Stock Android browser and email app were discontinued since KitKat :


Google puts Android’s stock e-mail app in the Play Store
Android 4.4+ KitKat ships without browser app. OEMs have to license Chrome or build their own


They have been replaced by Gmail and Chrome as commented. Even if you are willing to face security risk to have it installed you can't downgrade from Nougat to KitKat (extremely unlikely). Only option left is to run a device of pre KiKat OS having those stock apps