Go to Settings > Accounts & Passwords (for older iOS: Mail) > Accounts > Tap Exchange Account > Delete Account
Next, reset your wireless network. Go to Settings > General > Reset > Reset Network Settings
Restart your device by pressing and holding the Sleep/Wake button until a red slider appears and slide the slider. Then turn your device on by pressing and holding the Sleep/Wake button until the Apple logo appears
Enter WiFi credentials and passwords again if requested
Add your Exchange Account again, go to Settings > Accounts & Passwords (for older iOS: Mail) > Accounts > Add Account
If you see a prompt that asks “Cancel, Trust or Continue,” select TRUST
For more outlook fix information here.