SPF record
Short definition
SPF is a DNS record that lists which servers are allowed to send email on behalf of a domain, blocking spoofed mail.
SPF, Sender Policy Framework, is a TXT record added to a domain's DNS settings that explicitly lists the servers authorised to send mail for that domain. The receiving server checks incoming mail against that list.
Mail arriving from outside the list is treated as suspicious and may land in spam or get rejected outright. This makes it harder for anyone to send fake email pretending to be from the company.
SPF alone is not enough, paired with DKIM and DMARC it verifies sender identity across three layers. Updating the SPF record is an easy step to forget whenever a new email tool is added.
A common mistake is adding more than one SPF record to a domain, the standard allows only a single SPF record and a second one can invalidate the whole check. Piling too many providers into the include mechanism is another, since SPF only allows up to ten DNS lookups in total, and going past that limit causes the record to fail outright.
Why it matters
Mail sent from a domain with a missing or outdated SPF record increasingly lands in spam at Gmail and Outlook. Getting it right is a precondition for email actually reaching the customer.
Illustrative example
A workwear manufacturer switched to a new marketing tool and forgot to update its SPF record, some campaign emails landed straight in spam.
