Glossary · Cold email
What are SPF, DKIM and DMARC?
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Definition
SPF / DKIM / DMARC: Three DNS-level email authentication standards that tell receiving inbox providers your messages are legitimately from your domain. All three should be configured for any cold-email sender.
SPF (Sender Policy Framework) lists which servers are authorized to send from your domain. DKIM (DomainKeys Identified Mail) cryptographically signs each message so recipients can verify it wasn't forged. DMARC (Domain-based Message Authentication, Reporting, and Conformance) tells inbox providers what to do with messages that fail SPF/DKIM (reject, quarantine, or allow). All three live in DNS TXT records.
What is SPF?
Sender Policy Framework is a DNS TXT record listing the servers allowed to send email for your domain. Receiving servers check the sending server against that list. If you send through a new tool or mailbox provider, add it to the record, or mail from that service can fail SPF. SPF is defined in RFC 7208.
What is DKIM?
DomainKeys Identified Mail adds a cryptographic signature to each message. The receiving server looks up your public key in DNS and checks the signature, which proves the message came from your domain and wasn't altered in transit. Each sending service usually gives you its own DKIM record to publish. DKIM is defined in RFC 6376.
What is DMARC?
DMARC tells receiving servers what to do when a message fails SPF and DKIM alignment: nothing (p=none), send it to spam (p=quarantine) or reject it (p=reject). It also lets you receive reports on who is sending as your domain. Most teams start at p=none, review the reports, then tighten. DMARC is RFC 7489.
Do you need all three for cold email?
Set up all three. Gmail requires SPF or DKIM from every sender and DMARC from bulk senders above 5,000 messages a day, and receivers increasingly treat unauthenticated mail as suspect. For cold outreach, aligned SPF, DKIM and a DMARC record are the baseline before you think about copy or volume.
Related terms and pages
- Email deliverability
- The share of sent emails that actually reach the recipient's inbox (vs. spam folder, blocked, or bounced).
- Warm-up (email)
- Gradually increasing the daily send volume from a new email mailbox or domain to build sender reputation with inbox providers such as Gmail and Outlook.
- Cold email
- Unsolicited outbound email to prospects who haven't opted in, sent for B2B sales, recruiting or partnership purposes. Legal in many jurisdictions under specific conditions; ineffective without deliverability infrastructure.
Sources
- 1RFC 7208: Sender Policy Framework (SPF)Checked 23 Oct 2026
- 2RFC 6376: DomainKeys Identified Mail (DKIM)Checked 23 Oct 2026
- 3RFC 7489: DMARCChecked 23 Oct 2026
- 4Gmail Help: Email sender guidelinesChecked 23 Oct 2026
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