gmail android app

There are apps that password-protect individual apps. Look for

app lock

in the Play store.

 

Go into your phone settings and go to the Security section and choose the "Encrypt Device" option.

 

Go into the app settings and make sure you alow the app to be the administrator. Or enable stealth mode within the app settings.

Or download CloudMagic email client for android. It has a password protected options and it's also for all your email accounts. Like yahoo, Gmail, aol, imap, etc

 

Things I do on my primary devices with GMail, my information, etc:

-System PIN
-Encryption
-Use a ROM (I think Samsung does by default, as does OmniROM, and possibly just Android 4.1.x and newer) that doesn't mount internal storage until you unlock the device
-App Locker will lock individual apps. I've locked Settings and the Play Store on my Galaxy Victory "mp3" player since there's no screen lock, so unlockign it is difficult, at best.

 

Another partial layer of protection is ability to track, lock or wipe your device when lost.
You may have heard of apps like Where's My Droid. There are a bunch of them.
Also Google Device Manager:
https://play.google.com/store/apps/details?id=com.google.android.apps.adm&hl=en