Если 2012 можно через через PowerShell
$ConnectionBroker = ""
$SessionHostCollection = "Терминал"
$MessageTitle = "От кого)) "
$MessageText = "Текст "
If ($ConnectionBroker -eq "") {
$HAFarm = Get-RDConnectionBrokerHighAvailability
$ConnectionBroker = $HAFarm.ActiveManagementServer
}
$Sessions = Get-RDUserSession -ConnectionBroker $ConnectionBroker -CollectionName $SessionHostCollection
ForEach ($Session in $Sessions) {
Send-RDUserMessage -HostServer $Session.ServerName -UnifiedSessionID $Session.UnifiedSessionID -MessageTitle $MessageTitle -MessageBody $MessageText
}