Glossary
What is SPF, DKIM and DMARC?
SPF, DKIM and DMARC are the three email standards that let a receiving server check whether a message really comes from the domain in its From address.
An email's From line is only text. RFC 7208, the SPF standard published in April 2014, notes that email protocols place no restriction on the sender address a sending host can claim. SPF lets a domain list the servers allowed to send for it, DKIM (RFC 6376, September 2011) adds a signature the receiver can check, and DMARC, republished on the IETF Standards Track as RFC 9989 in May 2026, passes only when an SPF or DKIM pass lines up with the domain in the From header.
The NCSC tells organisations to move to a DMARC policy of reject once SPF and DKIM are working, and since 1 February 2024 Google has required anyone sending more than 5,000 messages a day to Gmail accounts to publish a DMARC record.
This matters for email to SMS, where an email becomes a text. CaptiFi Connect's email to SMS works from verified addresses only, so treat each address on that list the way you'd treat a login to your texting account.
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