If you have been listed in ecn.bgc.com.au then please contact your firewall vendor for a fix or replace the firewall and then re-test for automatic removal.
The "Reserved for Future Use" in RFC 791-1981 meant just that. The "currently unused" of RFC 2474-1998 also has a similar meaning. It has never meant "reserved, must be zero". Since RFC 3168-2001 its use has been defined and this is what it was reserved for. Packets with this set must not be dropped or damaged by vintage implementations that do not handle ECN.
September 1981
Internet Protocol
Specification
Type of Service: 8 bits
The Type of Service provides an indication of the abstract
parameters of the quality of service desired. These parameters are
to be used to guide the selection of the actual service parameters
when transmitting a datagram through a particular network. Several
networks offer service precedence, which somehow treats high
precedence traffic as more important than other traffic (generally
by accepting only traffic above a certain precedence at time of high
load). The major choice is a three way tradeoff between low-delay,
high-reliability, and high-throughput.
Bits 0-2: Precedence.
Bit 3: 0 = Normal Delay, 1 = Low Delay.
Bits 4: 0 = Normal Throughput, 1 = High Throughput.
Bits 5: 0 = Normal Relibility, 1 = High Relibility.
Bit 6-7: Reserved for Future Use.
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| | | | | | |
| PRECEDENCE | D | T | R | 0 | 0 |
| | | | | | |
+-----+-----+-----+-----+-----+-----+-----+-----+
Precedence
111 - Network Control
110 - Internetwork Control
101 - CRITIC/ECP
100 - Flash Override
011 - Flash
010 - Immediate
001 - Priority
000 - Routine
The ecn.bgc.com.au DNS list returns an A RR and a TXT RR. The A RR starts with 127. The next 2 bytes are the port. The value of the last byte is 8 if the port blocks ECN (TCP/IP). For example 127.0.25.8. An example script is here.
This may be merged with other lists. For example the last byte may be 2 if a spam complaint has been received, but as we do not care from which port the peer was bound the middle bytes will be zero. For example 127.0.0.2.