Glad to see you find the correct one. If the above suggestion helps, please feel free to accept it as an answer to close this thread. It also could be beneficial to other community members reading this thread.
I notice this one:
I think I will have a great job to update every user account to the new parameter...
You could use the command below to check whether one of them enabled for mailboxes:
Get-Mailbox -RecipientTypeDetails UserMailbox -ResultSize Unlimited | Get-CASMailbox | where {$_.ActiveSyncEnabled -eq $True -or $_.OWAEnabled -eq $true -or $_.PopEnabled -eq $true -or $_.ImapEnabled -eq $true}
If you want to disable them for those mailboxes, you could use the command below to disable them (It will disable those 4 protocols for all mailboxes):
Get-Mailbox -RecipientTypeDetails UserMailbox -ResultSize Unlimited | Get-CASMailbox | where {$_.ActiveSyncEnabled -eq $True -or $_.OWAEnabled -eq $true -or $_.PopEnabled -eq $true -or $_.ImapEnabled -eq $true} | Set-CASMailbox -ActiveSyncEnabled $false -OWAEnabled $false -PopEnabled $false -ImapEnabled $false
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