SPF record checker

What SPF is

SPF is a TXT record on your domain listing who is allowed to send mail on its behalf. The receiving server compares the sending address against that list. A match means the sender check passed; otherwise DMARC decides what happens next.

There is one record per domain, and it looks like this:

v=spf1 include:_spf.google.com ~all

The ten-lookup limit

The most common and least visible way SPF breaks. Every include, a, mx, ptr, exists and redirect costs a DNS lookup, and there can be no more than ten. On the eleventh the checker must return permerror — and the record stops working entirely, together with every sender you listed in it.

It usually breaks later, not on the day you edit it: you add one more service, it brings its own nested includes, and the total crosses ten. Mail starts landing in spam a week later, with nobody left to connect it to that edit.

The tail: ~all or -all

• -all — strict: reject anything not on the list. The right end state, but switch to it once you are sure you have listed everyone who sends as you, including mailing services and your CRM.
• ~all — soft: mark as suspicious. A sensible place to sit while you collect DMARC reports and hunt for forgotten senders.
• ?all — decide nothing. For a domain that sends mail this is the same as having no SPF at all.
• +all — allow everyone. Worse than no record: you are stating outright that anyone may write as you.

Two records instead of one

The other classic: the domain moved to a new service and the old record stayed. The checker does not pick the better of the two — it returns permerror and rejects both. Several services belong in one record joined by include, not in a second TXT.

Where MailSharks fits

If you send through your own Gmail, Google already owns and maintains that SPF — it is theirs, not yours. This check is for something else: your own domain, the one you write from (you@company.com), when its mail runs on Google Workspace or another provider.

Other checks

All three work without signing up and store nothing. For the bigger picture on deliverability see staying out of spam and Gmail limits.