1. On your iPhone, go to Settings  and Passwords and Accounts (on older iphones, it's settings and mail)
  2. Go to Add Account
  3. Choose Exchange
  4. Fill in your details. The description can be anything you want it to be
  5. Tap Next
  6. You should get a small window pop up asking you to configure manually or sign in. Tap Sign in.
  7. Wait while it says "verifying" 
  8. On the next screen, type your password when prompted and tap next.
  9. If you get a message that it cannot verify server identity, tap continue
  10. You may get a screen prompting for a server, domain and user name. These MUST be filled in as follows:
    • Server:  mail.pushex.com
    • domain: pushex
    • Username: <your email address>
  11. Tap Next
  12. You should see several tick-marks appear; make sure calendar is selected if it isn't already.  Now click Save


That's it