If you send an email using Outlook, there are two optional checkboxes that can be checked:
1. Request a delivery receipt for this message.
2. Request a read receipt for this message.
If you check "delivery receipt", the "Return-Receipt-To" header field is added to your email. For example:
Return-Receipt-To: "Chilkat Software"
If you check "read receipt", the "Disposition-Notification-To" header field is added to your email. For example:
Disposition-Notification-To: "Chilkat Software" <email@example.com>
The delivery receipt (i.e. Return-Receipt-To) is a request for the receiving mail server to send a DSN (delivery status notification) as soon as it receives the email.
The read receipt (i.e. Disposition-Notification-To) is a request for the receiving email client to send a DSN as soon as the person opens the email.
Both header fields can be added using the Chilkat Email object’s AddHeaderField method. For example:
email.AddHeaderField( "Return-Receipt-To" , "\"Chilkat Software\" <firstname.lastname@example.org>" );
email.AddHeaderField( "Disposition-Notification-To" , "\"Chilkat Software\" <email@example.com>" );
Setting the email.ReturnReceipt property is the equivalent of adding the Disposition-Notification-To field. (Sorry for the confusion. Unfortunately, that was a mistake made about 8 years ago…)