Also known as: Sender Policy Framework
An email-authentication standard that lets a domain list which servers are allowed to send mail on its behalf.
SPF (Sender Policy Framework) is a DNS record that publishes the list of servers authorised to send email for your domain. When a receiving server gets your mail, it checks whether the sending server is on that list. If not, the message can be treated as suspicious or forged.
SPF is one of the three core authentication standards alongside DKIM and DMARC. On its own it is limited — it breaks when mail is forwarded and only checks the envelope sender — which is why it is meant to be used together with the others.
Publishing a correct SPF record is table stakes for deliverability: major providers expect authenticated mail, and missing or broken SPF is a fast track to the spam folder.
An email-authentication standard that adds a cryptographic signature proving a message was not altered in transit.
A policy standard that builds on SPF and DKIM to tell receivers what to do with mail that fails authentication.
The ability of your email to actually reach recipients' inboxes rather than being blocked or filtered to spam.
See it in action
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