Not that it makes any difference, because I don't know, either way: But you want to enable requesting read receipts, or honoring requests for read receipts?
If it's the former, requesting read receipts, be advised that many email apps disregard that, and don't even have a configuration to enable generating read receipts. Personally, I've always found them invasive and offensive, so I've filtered read receipt requests out on any email server I've administered. I also always filter delivery receipt requests at the mail server.
They're also a security threat. Spammers and scammers can generate the malicious emails with "request read receipt" and automatically get notification their garbage was not only delivered, but read.