There aren't any Notes.ini settings that determine if the "Return Receipt" option is turned on or off by default. Remember that Notes IS NOT a dedicated "e-mail client" - your mail files are simply another Lotus Notes database application - so you are not bound by the restrictions placed on pure email applications like Outlook (as an example). Open the Database (Mail File) in Designer,
Open the "(Delivery Options)" subform,
Choose the "ReturnReceipt" field,
Give the field a default (text) value of "1" You have now turned on Return receipt by default for that mail file. If you specify this in the mail template (Mail50.ntf) it will change for ALL of your mail users - DO THIS WITH EXTREME CAUTION - it will place a hefty load on your mail server if EVERY message has RR turned on by default. ALTERNATIVE - Get your users to create a stationary item that has return receipt turned on. That way if they want this feature they simply choose "Tools -> New Memo Using Stationary" and then select the stationary with the RR turned on. Much Better Option!