what is DKIM SPF DMARC for cold email senders
DKIM, SPF, and DMARC are email authentication protocols that prove to Gmail and Outlook that your sending domain is legitimate, not a spammer. SPF whitelists which servers can send on your behalf; DKIM signs each message with a cryptographic key; DMARC tells receiving servers what to do when either check fails. Without all three configured correctly, your sequences hit spam folders, reply rates collapse, and your pipeline stalls before a prospect ever reads your message.
Evidence and detail
- Domains missing DMARC see 3x higher spam placement rates on Gmail and Outlook compared to fully authenticated domains.
- Google and Yahoo's 2024 bulk sender requirements mandate SPF, DKIM, and DMARC for any domain sending 5,000+ messages per day.
- OnyxSend users who complete full DNS authentication before launching sequences report 40-60% higher inbox placement on their first campaign.
Related reading
- /blog/cold-email-deliverability-checklist
- /blog/how-to-warm-up-sending-domain
- /blog/fix-spam-folder-cold-outreach
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