What happens when you change ESPs — how to migrate DKIM?

Question

Review My Emails · Accepted Answer

When you change sending platforms, you must create new DKIM keys in the new ESP and publish their corresponding public keys in DNS. Each ESP uses its own selectors and key pairs, so DKIM cannot simply be copied from the previous system.

The safe migration process is:

Create new selectors in the new ESP.

Publish the new TXT records in DNS.

Keep the old DKIM selectors live while traffic is still flowing from the old platform.

Move sending volume gradually to the new platform.

After all mail has moved, remove the old DKIM records.

This transition is much like moving your fleet from one harbor to another. You keep both harbors active for a short period so no ship is left without proper registration while the new pier takes over.