How to update DNS records during migration?

DNS updates during migration must be sequenced carefully to maintain authentication throughout the transition.

SPF record updates:

1. Add new ESP's include mechanism alongside old: v=spf1 include:old-esp.com include:new-esp.com -all

2. Verify SPF still passes (stay under 10 DNS lookups)

3. After migration complete, remove old ESP: v=spf1 include:new-esp.com -all

DKIM records:

1. Add new ESP's DKIM records (new selector, e.g., newsel._domainkey)

2. Both old and new selectors can coexist

3. Verify new DKIM signs correctly before sending

4. Keep old selector for a while after migration (forwarded emails may still verify)

5. Remove old selector after several weeks

Custom domains (bounce, tracking):

1. Set up CNAMEs for new ESP

2. Use different subdomains if needed (track2.yourdomain.com)

3. Update old CNAMEs after migration or maintain both temporarily

Timing considerations:

DNS changes propagate over time (TTL)

Lower TTL before migration for faster changes

Test changes propagated before relying on them

Make changes during low-traffic periods

Document all DNS changes for rollback if needed