Migrating transactional templates and webhooks from Resend to AutoSend — handling domain verification overlap

Migration Guides
1

We’re planning to migrate our transactional email sending from Resend over to AutoSend.

Since both services require CNAME records for DKIM and domain verification, can we add AutoSend DNS records alongside existing Resend records during a zero-downtime canary rollout, or will conflicting SPF/DKIM records break existing delivery?

2

You can achieve a 100% zero-downtime migration between Resend and AutoSend without any DNS conflicts.

Migration Steps:

  1. DKIM Selectors Do Not Conflict: AutoSend and Resend use distinct DKIM selector prefixes (e.g. resend._domainkey vs as._domainkey). You can add AutoSend’s DKIM CNAME records to DNS without affecting Resend.
  2. Combine SPF Records: Update your domain’s SPF TXT record to authorize both providers during transition:
v=spf1 include:amazonses.com include:autosend.com ~all
  1. Canary Traffic Rollout: Route 10% → 50% → 100% of transactional API requests to AutoSend while monitoring webhooks.
  2. Cleanup: After 7 days of 100% smooth delivery on AutoSend, safely remove Resend’s DKIM CNAMEs and SPF include tag.