SPF checker
Expand your sending sources, validate syntax, and count DNS lookups.
This SPF checker performs an SPF lookup on your domain and expands every include, a, and mx mechanism to show the full list of hosts authorized to send on your behalf. Crucially, it counts the DNS lookups your record triggers, because SPF must stay under 10 lookups or receiving servers may return a permerror and reject legitimate mail. You will also see whether your record ends in a sensible ~all or -all qualifier. Keeping that record accurate over time is where SJ Monitor's DNS monitoring helps, flagging changes as they happen.
Frequently asked questions
What is the 10 DNS lookup limit?
SPF evaluation is capped at 10 DNS lookups; exceed it and the result becomes a permanent error that can fail authentication. Flattening or consolidating includes is the usual fix.
What's the difference between ~all and -all?
~all (softfail) suggests unlisted senders are suspicious but may still be accepted, while -all (hardfail) tells receivers to reject them outright. Most domains move to -all once their sending sources are confirmed.
How do I know if a new vendor broke my SPF?
Adding includes can silently push you past 10 lookups. SJ Monitor's continuous DNS monitoring re-checks the record and alerts you when it changes or starts failing.
Can I have more than one SPF record?
No — a domain must publish exactly one SPF TXT record. Two SPF records cause a permerror and break authentication; merge all your sending sources into a single record instead.
What does the include mechanism do?
include pulls in another domain's SPF record (for example a provider's) and authorizes its senders for you. Each include counts toward the 10-lookup limit and may itself contain further lookups.
How do I fix exceeding the 10-lookup limit?
Remove unused includes, replace include chains with the specific ip4/ip6 ranges they resolve to (SPF flattening), or consolidate vendors. Keeping the record lean keeps it under the cap.
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