Do I understand correctly that you use the native mail- and photo apps?
Did you try restarting the photo- and email app?
-4finger swipe up or double tap the home button to show the last used apps, tap long on one until the red dot with the minus appears, then tap the minus to close the app
Restart the photo app and try to send it again.
If yes and still not working: did you restart the iPad?
-holding on/off (sleep) button to slide off the iPad, then switch it on again.
If yes and still not working: did you reboot the iPad?
-holding on/off button and home button at the same time until the unit switches off and the Apple appears again.
☠ stay safe ☠ stay legal ☠