DKIM is a DNS record that adds a digital signature to your emails, proving to inbox providers that the message is authentic and hasn't been tampered with.
DKIM proves email authenticity, preventing spoofing and tampering.
It's a critical DNS record, alongside SPF and DMARC, for building domain reputation.
An incorrect DKIM setup is a common and direct reason for landing in spam.
DKIM (DomainKeys Identified Mail) is an email authentication method that adds a digital signature to your outgoing emails. This signature is embedded in the email header and is secured with cryptography.
When a receiving mail server gets your email, it checks your DNS records for a public key that matches the signature. This process confirms that the email genuinely came from your domain and that its contents weren't altered in transit. For cold outbound, it's a non-negotiable part of proving your sending infrastructure is legitimate.
For teams sending thousands of emails, DKIM isn't just a technical detail—it's a core component of deliverability. Ignoring it is like trying to build a house without a foundation.
Setting up DKIM involves adding a specific record to your domain's DNS settings. It seems complex, but it's a straightforward process once you understand the components.
_domainkey. It includes a unique selector, like google._domainkey or s1._domainkey. This selector tells the receiving server which public key to look for, allowing you to have multiple DKIM records for different sending services.TXT record. The Host/Name will be the selector (e.g., google._domainkey), and the Value/Content will be the long string of characters provided by your email platform.A misconfigured DKIM record is often worse than having no record at all. Here are the most common failure points we see:
_domainkey as the host name is a frequent mistake. The name must match exactly what your sending provider specifies."...") to ensure it's treated as a single entry.Ultimately, teams sending cold outbound at scale need to understand DKIM. It's not optional. Proper authentication is the foundation of a healthy sending infrastructure, directly impacting whether your domains, inboxes, and reply rates stay healthy or get burned.
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