Sender Policy Framework or SPF is a necessary safety measure implemented by all major internet service providers to ensure safe communication by email.
To put it simply, SPF is a set of guidelines that outline which email sending apps and mail servers are allowed to send mail on your behalf. Basically, whenever a receiving server gets a message from you, it checks your DNS records. If there is an SPF record, it refers to this record and sees whether the incoming message complies with the policy. In case everything is alright, the message is allowed into the inbox.
This way, SPF prevents phishing, spoofing, and spamming, making users’ inbox a much safer place.