SpamAssassin Rule: RCVD_ILLEGAL_IP
Standard description: Received: contains illegal IP address
A check is made of the IP addresses listed in the Received lines in the mail header using RelayEval.pm. This test identifies IPv4 addresses that are invalid according the the allowable address space, as well as addresses that should never be seen as a source of mail.
The valid, but unusable, address ranges are as follows:
- 0/8 Reserved
- 1/8 Unallocated
- 2/8 Unallocated
- 7/8 Live allocation - US DoD
- 127/8 Loopback range (excepting localhost 127.0.0/24)
- 223/8 Unallocated
- 224/4 Multicast
Note that ranges currently marked "Unallocated" will probably be allocated by IANA at some point in the future.
Failure of this test suggests that the mailout software added extra message headers to disguise the real source of the message, or else is not using a professionally run network.
The default scores for this rule can be found in the online list of tests.
18.104.22.168/8 is allocated to the US Department of Defense. It was previously listed by IANA as 'Reserved' causing it to be added to "network bogon" lists. For its current use, it is not expected that traffic originating from this range will routed outside of this range. However, it's not clear that legitimate mail headers wouldn't contain IP addresses from this range.