According to the latest SPF specifications, for an IPv6 address the macro
"%{i}" produces a string in following format:
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.F.F.F.F.1.2.3.4.5.6.7.8
1.2.3.4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.F.F.F.F.1.2.3.4.5.6.7.8
This is useful for producing a domain name.
But for the explanation string we need a macro "%{c}" that produces a string
in following format:
::FFFF:18.52.86.120
1234::FFFF:1234:4567
Please add this additional macro letter to the SPF specifications.
Roger Moser