Without SPF, any server can claim to send as your domain. With a broken SPF record, legitimate mail fails authentication and lands in spam. SPF is also one of the two alignment paths DMARC relies on.
Mistake 1: Exceeding the 10-lookup limit, which causes a permerror and effectively disables SPF#
Why it hurts: this undermines SPF records at the point where mailbox providers make their decision, and it is rarely surfaced by your own tooling until placement drops.
Fix: Inventory every service that sends mail as your domain: your ESP, CRM, helpdesk, billing system, and internal mail server.
Mistake 2: Publishing two SPF records on one domain; receivers treat this as a permanent failure#
Why it hurts: this undermines SPF records at the point where mailbox providers make their decision, and it is rarely surfaced by your own tooling until placement drops.
Fix: Collect each vendor's SPF include mechanism (for example include:_spf.google.com) from their documentation.
Mistake 3: Forgetting that SPF checks the Return-Path (envelope sender), not the visible From address, so forwarded mail often fails#
Why it hurts: this undermines SPF records at the point where mailbox providers make their decision, and it is rarely surfaced by your own tooling until placement drops.
Fix: Publish one TXT record at the root of the domain starting with v=spf1, listing each include, then ending with ~all (softfail) while testing.
Mistake 4: Using +all or leaving ?all in production, which authorizes everyone#
Why it hurts: this undermines SPF records at the point where mailbox providers make their decision, and it is rarely surfaced by your own tooling until placement drops.
Fix: Verify with a lookup tool that the record resolves and stays under 10 DNS lookups and 255 characters per string.
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.