"Asking" for a return receipt (also known as a read receipt) is nothing more than adding an extra email header to your email. If you looked at the "full email headers" of an email that asks for a return receipt, you would see something like this:

Disposition-Notification-To: "Frank Smith" frank@thesmiths.com

To add that email header to an email you send with SMTPit Pro, all you need to do is use the "SMTPit_AddEmailHeader" function like this:

SMTPit_AddEmailHeader("Disposition-Notification-To='Frank Smith' frank@thesmiths.com")

Note, the equals sign ( = ) is used in the calculation, but when viewed in the recipient's email, you will see a colon ( : ).

Also note, a return receipt may not always work. This relies on the recipient's email client to send the receipt email. Some email clients will ask the user if they want to send the receipt email, while others may simply ignore the header, so it is possible you may not always get the receipt email depending on the recipient.