Rotate DKIM keys safely
rotate DKIM keys · DKIM key rotation · multiple DKIM selectors
A safe workflow for publishing a new selector, switching signing, waiting out TTL, and retiring the old DKIM key.
Autor: DN01 Network Team
DKIM rotation works best with two selectors: publish the new public key first, switch signing only after DNS is visible, then retire the old selector after mail queues and TTLs clear. DKIM potwierdza, że wiadomość została podpisana przez nadawcę, a klucz publiczny jest opublikowany w DNS.
Deleting the old selector too early breaks delayed mail, while switching signing before DNS propagation makes new messages fail verification. Sprawdź dokładną nazwę selector._domainkey.domena, bo bez selektora walidator nie wie, którego klucza ma użyć odbiorca.
Validate both selectors in /pl/dkim-validator, check TXT TTLs in /pl/dns-checker, and document the active selector before changing provider settings. Zweryfikuj TXT, tagi v/k/p/h/s/t, długość klucza, t=y i revoked, a potem porównaj wynik z DNS Checkerem.
What to verify first
Confirm that the selector is copied from the mail provider, not guessed from another domain or an old migration note.
Check whether the answer is a direct TXT record or a CNAME chain that eventually points at the DKIM TXT value.
Look at v=DKIM1, k=, p=, h=, s= and t= together. A record can exist but still be unusable when the public key is empty, malformed or too weak.
Common failure causes
The record was added to the wrong DNS provider, while the domain still delegates to another authoritative nameserver.
The selector changed during a provider migration, key rotation or domain re-verification, but an older selector is still being tested.
The TXT value was split or quoted incorrectly by a DNS editor, so receivers cannot reconstruct the base64 public key.
How to fix safely
Publish the new key first, wait for DNS visibility, then switch signing in the provider console. Do not delete the old selector until delayed mail has cleared.
Use t=y only during rollout. Once signed mail verifies consistently, remove testing mode so DKIM sends a stronger production signal.
Keep DKIM checks next to SPF and DMARC checks. A valid DKIM key is one part of deliverability, not the whole authentication policy.
| Tag | Why it matters |
|---|---|
| v=DKIM1 | Identifies the TXT value as a DKIM record. |
| p= | Carries the public key; an empty value revokes the key. |
| k= | Declares the key type, commonly rsa or ed25519. |
| h= | Limits allowed hash algorithms such as sha256. |
| t= | Flags testing mode (y) or strict subdomain behavior (s). |
Najczęściej zadawane pytania
- Can I check DKIM without a selector?
No. DKIM records are selector-specific, so you need the selector from your provider or from a DKIM-Signature header.
- Why is the DKIM record found but invalid?
The TXT record may have a wrong version tag, duplicate tags, missing p=, invalid base64, a revoked empty key or a weak/malformed public key.
- Should I keep the old selector during rotation?
Yes, keep it until TTLs and delayed mail queues clear. Removing it too early can break verification for messages already in transit.