Terms below appear throughout guides on SPF records. Each definition is one or two sentences; follow the links in the sidebar for the full guides.
Core terms#
SPF records
SPF (Sender Policy Framework) is a DNS TXT record that lists the servers allowed to send mail for a domain. Receivers check the connecting IP against that list during the SMTP transaction.
SPF
A DNS record listing servers authorized to send for a domain. Checked against the connecting IP.
DKIM
A cryptographic signature on each message, verified with a public key in DNS.
DMARC
A policy record telling receivers what to do when SPF and DKIM fail alignment, plus reporting.
Alignment
Agreement between the visible From domain and the domain that passed SPF or DKIM.
Sender reputation
A provider's running assessment of a domain or IP based on complaints, bounces, engagement, and authentication.
Inbox placement
Share of accepted mail that lands in the inbox rather than spam.
Spam trap
An address that never opted in, used to catch senders with poor list practices.
BIMI
A DNS record pointing to a brand logo displayed next to authenticated mail; requires DMARC enforcement.
Feedback loop
A provider program that reports recipient spam complaints back to the sender.
Frequently asked questions#
Does SPF alone stop spoofing?
No. SPF validates the envelope sender, which spoofers can set to their own domain while forging the visible From. DMARC closes that gap by requiring alignment.
What does ~all versus -all mean?
~all is softfail: receivers mark but usually accept. -all is hardfail: receivers may reject. Start with ~all, graduate to -all once DMARC data is clean.
How do I fix 'too many DNS lookups'?
Remove unused includes, replace includes with ip4/ip6 mechanisms where vendors publish static ranges, or use an SPF flattening service.