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Connect Cloudflare DNS to Mailstead and Resend
To use [email protected] in Mailstead, configure email delivery for example.com in Resend. To open webmail at inbox.example.com, configure that separate hostname in Railway. They are different DNS tasks.
Inspect existing mail routing first
Inspect the current MX records. If the domain receives mail through another provider, plan a migration before replacing its records. Keep the current values for rollback. A pilot on a separate subdomain can preserve the existing route, but its addresses will use that subdomain.
Do not mix unrelated MX targets to try to duplicate delivery. If Cloudflare forwarding or another provider currently receives the same domain’s mail, review that configuration first. The receiving domain needs the records specified by your selected receiving provider.
Configure the mail domain in Resend
Add the selected domain to Resend and configure both sending and receiving. Copy the exact record names, types, priorities, and values shown by Resend into Cloudflare DNS.
| Record | Purpose | Value to publish |
|---|---|---|
| Receiving MX | Route incoming mail | Current Resend receiving values and priorities |
| DKIM | Verify signed outgoing mail | Domain-specific values shown by Resend |
| SPF / sending records | Authorize transport | Resend’s instructions reconciled with existing senders |
| DMARC | Authentication policy and reporting | A policy appropriate to the actual domain senders |
Do not create two SPF records at the same name, guess a DKIM target, or replace an existing DMARC policy without reviewing its effect. Follow the provider’s DNS-only requirements for mail-related hostnames where Cloudflare offers proxying.
Wait for verification. A verified sending domain does not prove that inbound receiving is configured.
Configure the webmail hostname in Railway
Railway’s generated hostname works for the application while you test. For inbox.example.com:
- Add that hostname to the Mailstead service’s custom domains in Railway.
- Copy the exact DNS records Railway provides (including the CNAME target and any TXT verification record) into Cloudflare for the
inboxhostname. Start DNS-only while verifying the hostname and TLS. - Wait for Railway to confirm the domain and HTTPS.
- Set
PUBLIC_URL=https://inbox.example.com. KeepMAIL_DOMAIN=example.comif that is your mail domain. - Confirm the Resend webhook points to
https://inbox.example.com/hooks/resend.
Keep the existing website records intact. The website can stay on example.com while webmail runs on inbox.example.com.
Verify delivery
Create the exact recipient mailbox. Check /readyz, receive a message from an outside account, and reply to it. Confirm external receipt. If receiving fails, inspect MX and the webhook before changing unrelated website records.
Follow the complete setup checklist or give the guide to your coding agent.