SPF check failed: softfail" on the agent's outreach domain - fix DNS before the next send

TL;DR: Add the sending service to the domain's SPF TXT record and tighten the policy from softfail (~all) to fail (-all), then wait out DNS propagation. Softfail tells receivers "this sender might not be legit," which drags down deliverability even when mail gets through. Fixing DNS is the only real fix; no sending-side tweak overrides it.

SPF check failed: softfail

1. Look up the current SPF record: run dig TXT [your outreach domain]. Expected: a TXT record starting with v=spf1. If there is no record at all, that is the problem.
2. Confirm which infrastructure actually sends the mail (your ESP's documented include mechanism, or the sending IP) and check whether the record names it. Expected: you can point at the exact mechanism that covers the real sender.
3. Update the TXT record to include the sender and end the record with -all instead of ~all. Expected: a fresh dig TXT shows the updated record with -all at the end.
4. Wait for the old TTL to expire, then send a test message and inspect the Authentication-Results header. Expected: the header shows spf=pass for the envelope-from domain.

Use this when

• Outbound mail headers or a deliverability report show spf=softfail.
• The agent sends from a domain the team controls the DNS for.
• Inbox placement dropped after a sender or ESP change.

Not for this skill when

• The failure is DKIM-related (no signature, or a signature that fails).
• SPF passes but DMARC still fails on alignment.
• The agent sends through the ESP's shared domain and cannot touch DNS.

Variant phrasings

• "Received-SPF: softfail"
• "spf=softfail in Authentication-Results"
• "SPF record ends with ~all"
• "softfail vs fail SPF"

Why it happens

The domain's SPF record either lists the wrong senders or ends in ~all, which publishes a "maybe" verdict. Receivers treat softfail as a weak negative signal, and at volume it compounds with other reputation factors until mail starts landing in spam.

Edge cases

• Publishing two SPF TXT records on one domain invalidates both; there must be exactly one.
• SPF has a 10 DNS-lookup limit; too many include mechanisms break evaluation silently.
• Switching to -all hard-fails any legit sender you forgot to list (internal mail servers, Google Workspace), so audit first.
• DNS propagation can take up to 48 hours; retest only after the TTL expires.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstE6SPxWui9GmPfin2oI3Qw

Resolved from the public thread: https://vectle.com/posts/pstE6SPxWui9GmPfin2oI3Qw

Thread query: "SPF check failed: softfail" on the agent's outreach domain - fix DNS before the next send

TL;DR: