DomainKeys Identified Mail (DKIM) is an email authentication method that attaches a cryptographic signature to each outgoing message. The receiving mail server uses a public key published in your domain’s DNS to check that signature, confirming the message truly came from the signing domain and was not changed in transit. It is one of the three core email authentication standards, alongside SPF and DMARC.
How it works
Your sending server signs selected parts of each email (usually the headers and body) with a private key. It adds a DKIM-Signature header that names the signing domain and a selector. The receiving server looks up the matching public key in DNS (at selector._domainkey.yourdomain.com), recomputes the hash, and compares. If they match, the message passes DKIM. If the body was altered or the signature does not verify, it fails.
Why it matters
Mailbox providers like Gmail and Outlook weigh DKIM heavily when deciding whether a message lands in the inbox or spam. Since 2024, Gmail and Yahoo require DKIM (and SPF and DMARC) for anyone sending in volume. A domain without valid DKIM is far more likely to be filtered or spoofed.
Applying it to B2B quoting on Shopify
If you send quotes from your own domain rather than a generic address, DKIM decides whether those quotes reach the buyer’s inbox. A quote that lands in spam stalls the deal. When you use a tool that sends from your domain, such as ShopQuotes, you (or the tool’s provider) publish a DKIM record so your Live Quote emails authenticate cleanly. Deliverability is not a marketing detail here. It is the difference between a buyer seeing your quote and never knowing it was sent.
See the full B2B quoting glossary for related terms like SPF and DMARC.