Configure DKIM signing for your email domain

30 min Impact: high Effort: medium ✓ Scan-verified — no manual checkbox

DKIM adds a cryptographic signature to outgoing email that proves it genuinely came from your domain and wasn't altered in transit — receiving mail servers check this signature as part of deciding whether an email is legitimate or spoofed.

DKIM cryptographically signs every email you send so receiving servers can verify it actually came from you. Without DKIM, your emails have no proof of origin and are significantly more likely to land in spam.

The full picture

DKIM (DomainKeys Identified Mail) provides a genuine, cryptographic mechanism for verifying that an email message hasn't been altered in transit and genuinely originated from an authorized sender for your domain — this represents a meaningfully different and complementary protection to SPF, using digital signatures rather than sender-server verification alone.

The genuine mechanism here involves your mail server cryptographically signing outgoing messages with a private key, while a corresponding public key published in your DNS allows receiving mail servers to verify that signature — this verification confirms both that the message genuinely came from an authorized source and that its content wasn't tampered with after signing.

This cryptographic verification addresses a genuine gap that SPF alone doesn't fully close — SPF verifies the sending server but doesn't protect against message content tampering during transit, while DKIM's signature-based approach provides this additional layer of message integrity verification.

Together with SPF, DKIM forms a genuine foundation for comprehensive email authentication — receiving mail servers increasingly weight the presence and validity of both these protections when evaluating whether incoming mail claiming to be from your domain is genuinely trustworthy, making both protections' combined presence meaningfully stronger than either implemented alone.

How to fix it

1

Enable DKIM signing in your mail provider

Google Workspace, Microsoft 365, and most transactional email services have a DKIM setup section that generates the keys for you.
2

Add the DKIM DNS record they provide

Your provider gives you a specific TXT record (usually at a selector._domainkey subdomain) — add it exactly as given.
3

Verify it validates

Send a test email and check the headers, or use a DKIM validation tool, to confirm signing is actually active.
4

Repeat for every service that sends email as you

Each sending service needs its own DKIM setup — this isn't a single domain-wide switch.

Common mistakes

DKIM setup is per-SENDING-SERVICE, not a single domain-wide toggle — if you use both your main mail provider and a marketing tool, both need their own DKIM configuration.