Using SPF Record
According to RFC 7208, the Sender Policy Framework (SPF) is a DNS record that declares which host are, and are not, authorized to use a domain name for the "HELO" and "MAIL FROM" identity.
Through the years and after doing a lot of researches in the DNS best practises, the explorers have established that the TXT record is a better alternative for authorization of using the domain name identity. The SPF record still exists in the DNS hosting, but it must be published as a TXT record only.
Some of the DNS checkers continue to revise the DNS zone's file for SPF when there is a query for it. We recommend to our Customers, if they have to declare the authority for their domain name with SPF record, to create duplicated TXT and SPF records.