What’s the role of DNS in email delivery?

DNS (Domain Name System) is the phone book that makes email routing possible. When your ESP sends a message to subscriber@example.com, it first queries DNS for example.com's MX records (Mail Exchanger), which specify which servers accept mail for that domain. Without DNS, your ESP would have no idea where to deliver the message—like trying to mail a letter without an address.

DNS also stores your authentication records: SPF (TXT records listing authorized sending IPs), DKIM (TXT records containing public keys), and DMARC (TXT records defining your authentication policy). Receiving servers query your DNS during delivery to verify you're a legitimate sender. If these records are missing or misconfigured, your messages may fail authentication checks.

DNS is the silent foundation of email trust. Problems like slow DNS resolution can delay delivery. Incorrect MX records can cause complete mail loss. Authentication record errors result in failed SPF/DKIM checks. Most deliverability issues trace back to DNS at some point—always verify your DNS configuration when troubleshooting. Tools like MXToolbox and Google Admin Toolbox help diagnose DNS-related email issues quickly.