Email deliverability is one of the most underestimated problems in digital marketing. A business can have the most segmented list in the world, but if emails end up in spam, all the work is useless.
The three pillars of email authentication
First, you must have these three DNS records configured correctly: SPF, DKIM, and DMARC.
SPF (Sender Policy Framework)
A TXT record on your DNS declaring which servers are authorized to send email for your domain. Common mistake: having multiple SPF records — only one is allowed per domain.
DKIM (DomainKeys Identified Mail)
A cryptographic signature that verifies the email has not been altered in transit. Your ESP provides a public key to add to your DNS. Always verify DKIM is validated using tools like MXToolbox.
DMARC
The policy layer telling providers what to do with emails that fail SPF or DKIM. Start with a permissive policy (p=none), analyze reports for 30-60 days, then move to p=quarantine.
Key negative signals
- Bounce rate above 2%: remove hard bounces immediately
- Spam complaint rate above 0.1%: Google and Yahoo set this as a limit in 2024
- Low open rate: signals to providers that recipients don't want your emails
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