Thou shalt heed caution with “-all”, for a single misstep may close the gates of deliverability.
Does your SPF record need more than ten DNS lookups?
Ten is the limit, and crossing it means permerror: SPF stops
working and you are not told. Enter a domain to see what its record really
costs. If it is under the limit, we will say so and you can leave it alone.
What the change looks like, if you need it
Before five includes, and every one of them costs a lookup
costs one DNS lookup.
After one guru lookup and your own policy, everything else left exactly where it was
is what a receiver looks up. Everything
after the all is read by SPF Guru instead, and costs nothing.
A receiver resolves one name and stops: authorised senders match and pass,
everything else falls through to your own all. If SPF Guru
cannot answer, that is also just "no match", so your own policy still
decides rather than the record breaking. The rest is left untouched because
that is what SPF Guru reads on your behalf.
How that works.
Not flattening
Your includes stay includes, resolved at query time. Nothing goes stale when a vendor renumbers.
One lookup, always
Twelve includes or thirty, a receiver performs the same one and gets a definitive answer.
Nothing to install
One TXT record at your DNS provider. No agent, no account.