Security
SPF
Sender Policy Framework
Sender Policy Framework (SPF) is an email authentication standard that publishes the list of IP addresses authorised to send mail on behalf of a domain. Mailbox providers reject mail from unlisted IPs.
In depth
SPF is published as a single DNS TXT record at the apex of the domain, listing IPs and includes (other domains' SPF policies that should be merged in). It has hard limits — no more than 10 DNS lookups during evaluation — that surprisingly many large senders quietly violate.
SPF alone is fragile: it breaks on email forwarding (the forwarder's IP is not on the original sender's SPF list). It is therefore always paired with DKIM and DMARC for a complete authentication stack.
Why it matters
Missing or misconfigured SPF causes legitimate marketing and transactional email to land in spam, killing conversion rates and customer notifications. It is also a prerequisite for DMARC enforcement.
How Lemwatch helps with spf
Lemwatch monitors spf continuously and alerts you the moment something changes.
Email deliverability →Related terms
DMARC
DMARC is an email authentication protocol that lets a domain owner publish a policy specifying how mailbox pro…
DKIM
DomainKeys Identified Mail (DKIM) is an email authentication standard that adds a cryptographic signature to e…
DNS
The Domain Name System (DNS) is the distributed database that translates human-readable domain names like lemw…
CSP
Content Security Policy (CSP) is an HTTP response header that restricts which sources a browser may load scrip…
HSTS
HTTP Strict Transport Security (HSTS) is an HTTP response header that tells browsers to access the site only o…
Browse the full Lemwatch monitoring glossary (47 terms).