Here are my findings:
1. Yes, the recipient mail server does support Read Receipts. I am getting a Read Receipt but it is not going to the address I specified, it goes to the "From address".
2 & 3. I understand the end user might have it turned off or choose not to send. The problem was not whether we received the Read Receipt or not but that it was ignorning the Header value that I specified.
4. I made this change and it still did not send the Read Receipt notification to the address I specified, just to the "From" address.
In addition I found out that you cannot set the DeliveryOptions as follows (even though the enum states that it is a flags attribute):
DeliveryOptions = OnSuccess OR OnFailure
When doing so the OnSuccess does not work.
1. Not setting the DeliveryOptions flag but manually adding the Disposition and Return headers does nothing, once sent those headers are stripped from the message. Neither Message Delivery or Read Receipt emails are sent.
2., Setting the DeliveryOptions flag to OnSuccess and not adding the headers manually results in the headers being added by the system and a Disposition and Return email address being set to the From address. Both MessageDelivery and ReadReceipt message are sent to the From address.
3. Setting the DeliveryOptions flag to OnSuccess and manually adding the headers with a different email address results in the manually added headers being ignored. Both Message Delivery and Read Receipt messages are sent to the From address.
4. Setting the DeliveryOptions flag to OnSuccess OR OnFailure results in no Message Delivery or Read Receipt message being sent.