Mail not working on new iOS 15 devices

We are unable to get email working on iOS 15 devices.  We use an EAS proxy for our email.  It works fine on iOS 14 devices.  If those iOS 14 devices with the email policy already applied and working are updated to iOS 15 - they still work fine.  However, if we push the email policy to an iOS 15 device for the first time, it doesn't work at all.  The device just states that it is "unable to verify account information".  There is no trace of the device checking in contained in the EAS logs on the server.

Comparing the mail settings on an upgraded, working device to a new non-working device, the mail/account settings appear to be identical, but the device that shipped with iOS 15 does not want to communicate with the EAS server.  I've tried with the new mail privacy settings enabled and disabled with no effect.

I feel like there has to be something tiny I'm missing that once I determine what it is will make feel like an imbecile for overlooking it Slight smile

Any help would be greatly appreciated.