title: Does "System.Net.Mail.DeliveryNotificationOptions" only work with Exchange?
body: <p>We have an application that is running on a SharePoint 2010 server that sends an email. We (the sender) want to receive delivery notifications but we are unable to retrieve them on the live system.</p>
  
  <p>I've set the <code>System.Net.Mail.DeliveryNotificationOptions</code> to <code>OnSuccess | OnFailure | Delay</code> and it is running fine on our internal test system. I receive the notifications in my inbox (which is the "from address" that I used). Internally we use Exchange 2007.</p>
  
  <p>At the customer site with the same solution no notifications are received. They don't use Exchange for the email delivery from SharePoint but some other SMTP server.</p>
  
  <p>Can it be that the delivery notificaiton option only works with MS Exchange? Or does it use a standard (well, it's Microsoft) that other mail servers also understand? The documentation doesn't mention any mail server requirements.</p>