Authentication
What is Email Authentication (SPF, DKIM, DMARC)?
The DNS-based protocols that prove an email genuinely came from your domain.
Email authentication is a family of standards that let receivers verify a message's origin and integrity. SPF authorizes which servers may send for a domain, DKIM cryptographically signs messages, and DMARC ties those results to the visible From domain and tells receivers how to handle failures. Mailbox providers evaluate all three as a baseline trust signal.
Why it matters for cold email
Since the Google and Yahoo bulk-sender rules took effect in 2024, unauthenticated mail is routinely rejected or spam-foldered, so SPF, DKIM, and DMARC are non-negotiable for cold outreach. Authentication is the foundation everything else sits on; without it, even perfect content and clean lists will fail to reach the inbox.
Related terms
Stop guessing at deliverability.
Scheduler Zero handles authentication, warmup, and sender reputation so your cold email lands in the inbox, not the spam folder.