DKIM adds a cryptographic signature to every email your domain sends. The receiving mail server checks the signature against a public key in your DNS. A valid signature proves the email genuinely came from you and hasn't been altered in transit.
Without DKIM, your emails carry no proof of origin. Receiving servers rely entirely on your reputation — and that reputation can be undermined by anyone else sending under your domain name.
What happens without it
- Google and Yahoo require DKIM for all bulk senders as of 2024 — non-compliance affects delivery
- DMARC enforcement is not achievable without DKIM or SPF alignment — you cannot close the spoofing gap
- Enterprise procurement questionnaires list DKIM as a required control; missing it blocks supplier approvals
- Email forwarding breaks SPF authentication — DKIM is the only authentication that survives being forwarded
What fixing it involves
DKIM configuration happens in two places: your email platform generates a key pair and gives you a DNS record (usually a CNAME or TXT), which you then publish at your domain registrar. The key pair ties your sending infrastructure to your domain.
The complication: every service that sends email on your behalf (your main email provider, your newsletter platform, your CRM, your billing system) needs its own DKIM key. A single DKIM record covers only the service that generated it.
What your domain scores right now
Run the free DomainScores check to see your current DKIM grade alongside 34 other security checks — instant, no signup.
Don't want to do this yourself? Domain Fix from €1,197 — we configure DKIM for every sending service, alongside DMARC, SPF, and every other failing check. Grade B+ guaranteed, or your money back.