Custom sending domain

What is a sending domain?

A sending domain is the domain used to send email notifications (the domain behind the Return-Path and Sender headers). Back in Stock uses secure default sending domains if you don’t set one — but adding your own domain improves brand trust and aligns with authentication policies like SPF, DKIM, and DMARC.

Why set up a custom sending domain?

Using a custom sending domain:

• Strengthens email authentication
• Helps meet strict DMARC policies (p=quarantine  or p=reject )
• Removes “via/backinstock…” labels in the inbox
• Improves deliverability and brand consistency

Note: This feature is available on the Startup plan and higher.

Recommended: Use a subdomain

We strongly suggest configuring a subdomain dedicated to Back in Stock email:

Example:

email.yourstore.com  (recommended)

instead of

yourstore.com  (not recommended)

Using a subdomain:

• Prevents conflicts if other services also use Mailgun

• Protects the deliverability reputation of your main domain

  (customer support and order emails remain isolated)

How to set up a custom sending domain

You can complete the entire setup within the Back in Stock app — no need to visit Mailgun.

Step-by-step

1. Go to: Settings → Custom domain → Add a custom domain

2. Enter the subdomain you want to use (e.g. email.yourstore.com )

   Click Verify domain

   A modal will display DNS records that must be added to your DNS host:

   • MX records
   • DKIM (TXT)
   • SPF (TXT)

   • CNAME

     DNS propagation may take up to 48 hours, but usually completes within minutes.

3. Click Verify once your DNS updates

   When all checks pass, the status will automatically update.

   Click Manage email settings to configure:

   • From email (must be inside your verified domain)
   • Reply-to email (should be a real inbox that receives replies)

4. Click Save email settings

   This saves the settings and automatically updates your sending domain.

Example configuration

Why MX records are required

Even if the domain only sends emails, MX records help prevent “Sender Domain Verification” errors that some receiving servers enforce.

Verifying authentication

You can inspect email headers to ensure your configuration passes SPF, DKIM, and DMARC checks:

https://toolbox.googleapps.com/apps/messageheader/

Need help?

If DNS records have not verified after 48 hours, please contact backinstock-support@useamp.com for assistance.

Last updated: December 2025