- Typical settings include:
True always allow a return receipt False never allow a return receipt fun apply fun to determine whether to give a return receipt
- With the setting ReturnReceiptFunction->fun, fun is applied to the same association as in MailReceiverFunction, but with an additional entry "Result" that gives the result from applying the function in MailReceiverFunction.
- The function fun is only applied if a return receipt was requested for a particular piece of mail, as indicated by the value for "ReturnReceiptRequested" in the association supplied to MailReceiverFunction.
- If the value obtained by applying fun is True, a return receipt is given; otherwise, it is not.
Introduced in 2015