with a lot testing with mobile device, i reached again the maximum number of allowed mobiles devices to sync with exchange environment via active sync
You have 100 device partnerships out of the maximum allowed 100 partnerships. After you reach the maximum, you can’t create additional partnerships until you delete existing ones from your account. To do this, sign in to Outlook Web App, click Options > Phone > Mobile Devices, and delete any unused partnerships.
when logged in via webmail it is possible to remove the paired devices via selfservice, unfortunately it is just possible to remove each device by itself in a not very performant ui
as an admin there a other ways to get around this limitation via powershell
change the limit and increase the number – execute
Get-ThrottlingPolicy | Set-ThrottlingPolicy -EASMaxDevices 20
programatically remove paired mobile devices
Get-MobileDeviceStatistics -Mailbox "tonysmith" | Format-Table DeviceType, FirstSyncTime, LastSuccessSync, Guid