Speaking in terms of standards, record checks should include type SPF=20
records along with type TXT. SPF checkers are supposed to look for=20
either record type.
Resource Record type 99 to was assigned as SPF by the IANA, in July=20
2005. This is intended to replace the use of TXT records, although both =
are valid and it will admittedly be many years before (if ever) TXT=20
record use is phased out.