Sender Policy Framework (SPF) records are used to specifying which email servers are permitted to send email on behalf of a given domain name. Correct configuration of SPF records is important to prevent recipients marking your email as 'junk'.
The DNS RFCs originally introduced a new 'SPF' record type to support this scenario. To support older name servers, they also permitted the use of the TXT record type to specify SPF records. This ambiguity led to confusion, which was resolved by RFC 7208. This states that SPF records should only be created using the TXT record type, and that the SPF record type is deprecated.
SPF records are supported by Azure DNS and should be created using the TXT record type. The obsolete SPF record type is not supported. When importing a DNS zone file, any SPF records using the SPF record type are converted to the TXT record type.