How do I undo return receipt requested?
Disable adding the header to your outbound e-mails that requests a read
receipt from the sender. Do NOT add the read receipt request to your
outbound e-mails.
A header gets added to your e-mail that asks the recipient's e-mail
client to send back a read receipt. The recipient may or may not send
back a new e-mail that comprises the read receipt. They may get
prompted and say No. They may permanently disable acknowledging or
prompting on read receipt requests.
Once you send an e-mail, it is no longer under your control. You can
hope the recipient has their tracking options in Outlook configured to
always ignore read receipt requests. From now on, just don't add the
header to your outbound e-mails. Configure Outlook to NOT ask for read
receipts.