This is a post by Paul at the sysadmin channel
If you have tried to install Remote Server Administration tools for Windows 10 version 1809, 1903 or later you might have come across: Add-WindowsCapability failed. Error code = 0x800f0954. If you haven’t, that’s great! If you have, you’re in luck because today we’re going to go over the steps needed to fix the issue.
Apparently Exchange 2010 SP1 brought a 10 mobile device per mailbox limit. This is a problem if you are letting a bunch of folks hook their iPhones into a common mailbox to share the calendar. The mailbox gets the message:
You have 10 phone partnerships out of the maximum allowed 10 partnerships. After you reach the maximum, you can't create additional partnerships until you delete existing ones from your account. To do so, sign in to Outlook Web App, click Options > Phone > Mobile Phones, and delete any unused partnerships.
Fortunately, the fix is pretty simple (excellent full write-up here), if you just want to increase the number of devices for your default policy.
Alternativelly, you can remove all partnertships for a mailbox with the following command:
foreach ( $identity in Get-ActiveSyncDeviceStatistics -Mailbox username | Select-Object -Property "Identity" ) {
Remove-ActiveSyncDevice -Identity $identity.identity -Confirm:$true
}
Also you can remove all device partnerships where synchronization date (LastSuccessSync) is more than 30 days ago:
$DevicesToRemove = Get-ActiveSyncDevice -Result Unlimited | Get-ActiveSyncDeviceStatistics | Where {$_.LastSuccessSync -le (Get-Date).AddDays(“-30”)}
$DevicesToRemove | Remove-ActiveSyncDevice
