foo.org 1 IN TXT "v=spf1 include:_spf.google.com include:_spf.bar.com ~all"
foo.org 1 IN TXT "v-spf1 ip4:99.99.99.99 包括：_spf.google.com ~all"
还是因为对谷歌的两次引用而需要将它们合并为一个记录？
domain-name-system spf txt-record
domain-name-system ×1
spf ×1
txt-record ×1