This is my inofficial, unsupported patch to
re-enable 'Return-Receipt-To:' in sendmail 8.7.3.

*** envelope.c  Thu Dec  7 11:54:33 1995
- --- envelope.c.new    Thu Dec  7 11:51:06 1995
***************
*** 263,272 ****
        **  Send back return receipts as requested.
        */

! /*
        if (e->e_receiptto != NULL && bitset(EF_SENDRECEIPT, e->e_flags)
            && !bitset(PRIV_NORECEIPTS, PrivacyFlags))
! */
        if (e->e_receiptto == NULL)
                e->e_receiptto = e->e_from.q_paddr;
        if (success_return && !failure_return &&
- --- 263,275 ----
        **  Send back return receipts as requested.
        */

!       /* re-enabled, ca, 07.12.1995   */
        if (e->e_receiptto != NULL && bitset(EF_SENDRECEIPT, e->e_flags)
            && !bitset(PRIV_NORECEIPTS, PrivacyFlags))
!       {
!               success_return = TRUE;
!       }
!
        if (e->e_receiptto == NULL)
                e->e_receiptto = e->e_from.q_paddr;
        if (success_return && !failure_return &&