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    Authentication

    SPF (Sender Policy Framework)

    A DNS record that lists which servers are allowed to send email on behalf of your domain.

    SPF lets you publish a list of servers (by IP or hostname) that are authorized to send mail using your domain. When an inbox provider receives a message, it checks the sender IP against your published SPF record. If it does not match, the message can be rejected or flagged as spam. SPF alone is no longer enough for serious senders — pair it with DKIM and DMARC.

    Related terms

    DKIM (DomainKeys Identified Mail)

    A cryptographic signature added to outgoing emails that proves the message really came from your domain and was not tampered with.

    DMARC

    A policy you publish in DNS that tells inbox providers what to do if SPF or DKIM checks fail.