What problem was SPF created to solve?

SPF was created to stop attackers from sending mail using someone else’s domain at the envelope level. Before SPF, anyone could send a message claiming to be captain@tidalmail.com, and servers had no way to verify this.

SPF addresses the specific problem of envelope from spoofing, also called Return Path spoofing. It does not protect the visible From line, which is why SPF alone is never enough.