header should never be declared in the configuration file and, in
fact, should rarely be used at all. It is not intended as a routine
delivery-verification mechanism, but rather is intended for
occasional use in debugging delivery problems. It is especially
dangerous when used in outgoing mailing-list mail because it can
cause an avalanche of returned mail and can possibly bring a host to
Beginning with V8.6 sendmail, a receipt is sent
when the mailing list is first expanded, and the
Return-Receipt-To: header is removed before
forwarding the message to the list.
Beginning with V8.7 sendmail, processing of all
Return-Receipt-To: headers can be skipped by
specifying noreceipts with the
PrivacyOptions option (PrivacyOptions).
Return notification is triggered by NOTIFY=SUCCESS extension (-N) to the RCPT TO: command.
If the PrivacyOptions option's
noreceipts (See this section) keyword
is specified, no success return notification will be sent. Beginning
with V8.10, if the RrtImpliesDsn option (RrtImpliesDsn) is set, the presence of a
Return-Receipt-to: header will cause
sendmail to act as if NOTIFY=SUCCESS was
specified, even if it was not. In this instance, the value of the
Return-Receipt-to: header is ignored. Other than
with the RrtImpliesDsn option, the
Return-Receipt-to: header is otherwise ignored.