Custom domains let you create inboxes on addresses you control (for example ) while still using MailSlurp APIs for send, receive, and test automation.

Before you start

You need:

  • A domain you own.
  • Access to its DNS provider.
  • A MailSlurp plan that supports custom domains.

Setup flow

  1. Open the MailSlurp dashboard.
  2. Add your domain in domain settings.
  3. Copy the DNS records MailSlurp provides.
  4. Publish records at your DNS provider.
  5. Wait for verification to complete.

MailSlurp only verifies once per domain. After verification, you can create many inboxes under that domain.

DNS records to verify carefully

Most setups require a combination of:

  • MX records for receiving mail.
  • SPF records for sender authorization.
  • DKIM records for signing.
  • DMARC policy/monitoring records.

If you already have email in production, avoid destructive replacement. Merge records safely and test gradually.

Common rollout mistakes

  • Removing existing production MX/SPF records too early.
  • Publishing duplicate SPF policies instead of merging.
  • Forgetting DKIM selectors for the new sender path.
  • Testing only send-path and skipping receive-path assertions.
  • Stage in non-production first.
  • Create one or two validation inboxes.
  • Run send + receive + webhook checks.
  • Confirm DMARC/SPF/DKIM behavior.
  • Expand inbox provisioning after stable results.

Next step

After domain verification, create a dedicated test inbox and run one full signup or OTP flow through Email Sandbox.