Da es in Powershell eine Implementation für REST gibt, muss man nicht den Umweg über den .NET WebClient gehen.
$json = @{ AuthorizationToken = "44xx44x444x44xxxxx4xxx444x444xx"; Body = "Body 12345...."; Title = "Titel der Nachricht"; Link = "https://www.google.de"; LinkTitle = "Google"; Source = "Powershell"; TimeToLive = "60" } | ConvertTo-Json $uri = "https://pushalot.com/api/sendmessage" Invoke-RestMethod -Method Post -Uri $uri -ContentType "application/json" -Body $json