Return receipts ALWAYS sent even when turned off

[nedb]

Thunderbird 38.3.0
Windows 10

Regardless of how I set the choices for return receipts, and no matter where I set them (Global or per account), Thunderbird is now always sending a receipt, even if I tell it never to send a receipt. I know this because I include myself in messages where I want a return receipt from other recipients. As soon as I read the message that comes to me, without even being asked, a return receipt is sent to me. This is a serious issue in that many spammers use the return receipt function to see if 'anyone is home' and now there is no way of controlling this. As soon as you open up a message that got by spam filters, a return receipt is sent if it was requested.

What can be done to truly control return receipts, even if I just have to turn them off (which is not working as I said above)? I have even tried the add on "NewReturnReceiptHandler 0.4.11" and that does absolutely nothing.

[DanRaisch]

Use menu path Tools->Options->Advanced->General tab->click on "Config Editor"->enter "receipt" into the filter bar. For both mail.identity.default.request_return_receipt_on and mail.receipt.request_return_receipt_on, is the displayed value "False"?

[nedb]

Yes, both values are listed as "false".

[DanRaisch]

Try toggling those to "True", closing and restarting Thunderbird, and then switching them back to "False", repeating the close restart cycle.

[nedb]

Thanks, but I did exactly what you suggested with exactly the results I got before: a message to myself with return receipt requested does not allow for a choice and immediately sends a receipt upon reading the message.

Surely there has to be a way of resolving this issue.