IOS devices and Exchange won't connect over Wifi

Neither my ipad nor my iphone 5 will connect with my exchange server over my wifi network. The problem is limited to IOS devices on wifi and Exchange. The phone will connect with exchange over the cellular network. My windows laptop works fine over wifi with exchange and everything else. The ipad and iphone will connect to wifi and have no problems with web browsing, gmail, etc. I've used both devices successfully for months and the problem started yesterday. I did not do any IOS updates yesterday.

iPad and iPhone are both on IOS 7.0.4

The message on the screen: Cannot Get Mail. Server error. Contact your server administrator.

It also says: Cannot Get Mail. The connection to the server failed.

What I've tried:

• Resetting network settings (only tried on iPad, since it didn't work)
• Powering off each device then turning back on
• Powered down the wireless router and powered back up
• Confirmed with the exhange hosting company (GoDaddy) that they've made no changes