Custom Sender Domain

By default, LostChurn sends dunning emails from a shared sending domain. Setting up a custom sender domain improves deliverability, builds brand trust, and gives you full control over your sender reputation.

LostChurn offers two paths for domain onboarding:

Why Use a Custom Domain?

Path A: Auto-Provision (Instant Setup)

The fastest way to get a dedicated sending domain is to auto-provision a LostChurn subdomain. LostChurn creates a subdomain under send.lostchurn.com using your merchant slug (e.g., acme.send.lostchurn.com) and handles all DNS configuration automatically.

How It Works

1. Navigate to Settings > Email > Custom Domain
2. Click Auto-Provision Domain
3. Confirm your From Name, From Email, and optional Reply-To address
4. LostChurn creates the subdomain in Resend and adds the required CNAME records to the lostchurn.com DNS zone via the Cloudflare API
5. The domain is verified and ready for warmup within seconds

What LostChurn Configures

When you auto-provision, LostChurn automatically:

• Creates the domain in Resend
• Adds DKIM, SPF, and return-path CNAME records to the lostchurn.com Cloudflare zone
• Verifies all DNS records
• Persists the domain configuration to the database
• Begins the warmup schedule

No manual DNS changes are required on your part.

Path B: Custom Domain (CNAME Delegation)

For full brand control, configure your own domain with CNAME delegation to Resend.

Step 1: Add Your Domain

1. Navigate to Settings > Email > Custom Domain
2. Click Custom Domain Setup
3. Enter the domain you want to send from (e.g., mail.yourdomain.com)
4. Configure your From Name, From Email, and Reply-To address
5. Click Add Domain

Step 2: Add DNS Records

After adding your domain, LostChurn displays the CNAME records you need to add to your DNS provider. LostChurn uses CNAME-based delegation through Resend, which automatically handles SPF and DKIM signing.

You will see three CNAME records in the dashboard:

Return-path records are proxied through send.lostchurn.com for consistent SPF alignment across all LostChurn customers.

Copy each record from the dashboard and add it in your DNS provider (Cloudflare, Route 53, GoDaddy, Namecheap, etc.).

Step 3: Verify DNS

After adding the records, return to Settings > Email > Custom Domain and click Verify DNS. LostChurn checks each record and updates the verification status:

The verification endpoint checks SPF, DKIM, and DMARC records and returns detailed results:

{
  "success": true,
  "status": "Verified",
  "spf_verified": true,
  "dkim_verified": true,
  "dmarc_verified": true,
  "diagnostics": { "spf": {}, "dkim": {}, "dmarc": {} }
}

DNS propagation typically takes 1-2 hours but can take up to 48 hours in some cases. You can click Verify DNS again at any time to recheck.

Step 4: DMARC (Recommended)

While not required by LostChurn, adding a DMARC record improves deliverability and gives you visibility into email authentication results. Add a TXT record:

_dmarc.yourdomain.com  TXT  "v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com"

Start with p=none (monitoring only) and move to p=quarantine or p=reject once you have confirmed all legitimate email sources are authenticated.

Domain Warmup

New sending domains have no established reputation with inbox providers. Sending a large volume of email from a new domain immediately would trigger spam filters. LostChurn automatically warms up your domain by gradually increasing the daily sending limit over 22 days:

During warmup, if your daily volume exceeds the current phase limit, LostChurn falls back to the default shared sending domain for the overflow emails. This ensures your customers still receive recovery messages while the domain reputation builds.

Tips for Successful Warmup

• Start with engaged recipients -- during the warmup period, prioritize sending to customers who have previously opened or clicked your emails
• Keep content clean -- avoid spam trigger words and maintain a good text-to-image ratio
• Monitor bounce rates -- if your bounce rate exceeds 5% during warmup, review your email list quality
• Be patient -- rushing the warmup damages long-term deliverability

Configuring the Sender Identity

Once your domain is verified (or during warmup), configure how your emails appear to recipients:

The From Email must use the verified domain. The Reply-To address can be any valid email address -- it does not need to be on the same domain.

Removing a Custom Domain

To remove a custom domain and revert to the default LostChurn sender:

1. Go to Settings > Email > Custom Domain
2. Click Remove Domain
3. Confirm the action

After removal, all campaign emails will be sent from the default LostChurn sending address. Your DNS records can be safely removed from your DNS provider.

Domain Diagnostics

LostChurn provides a diagnostics endpoint that runs live DNS checks against your domain at any time. Access it from the dashboard or via the API:

curl https://edge.lostchurn.com/api/email-domain/status/{merchant_id} \
  -H "Authorization: Bearer lc_live_your_api_key"

The response includes your domain configuration, warmup status, and live diagnostics:

{
  "domain": {
    "id": "sd_abc123",
    "domain": "mail.yourdomain.com",
    "domain_type": "CustomDomain",
    "status": "Active",
    "spf_verified": true,
    "dkim_verified": true,
    "dmarc_verified": true,
    "warmup_daily_limit": null,
    "warmup_started_at": "2026-02-19T00:00:00Z",
    "created_at": "2026-02-19T00:00:00Z",
    "verified_at": "2026-02-19T01:30:00Z"
  },
  "diagnostics": { "spf": {}, "dkim": {}, "dmarc": {} },
  "cached": false
}

For verified domains, diagnostic results are cached in edge KV to reduce DNS query load. The cached field indicates whether the result came from cache or a live check.

Troubleshooting

Next Steps

• Email Campaigns -- Create and optimize your dunning email templates
• Emails Not Delivering -- Troubleshoot delivery issues
• Engagement Analytics -- Monitor delivery rates and email performance