MX Records

To receive email with MXHook, you need to point your domain's MX (Mail Exchange) records at the server running MXHook.

Setup

Add an MX record to your domain's DNS:

Type	Name	Value	Priority
MX	yourdomain.com	mail.yourdomain.com	10
A	mail.yourdomain.com	YOUR_SERVER_IP	—

Replace YOUR_SERVER_IP with the public IP address of your MXHook server.

How It Works

When someone sends email to user@yourdomain.com:

1. The sender's mail server looks up the MX record for yourdomain.com
2. The MX record points to mail.yourdomain.com
3. The A record resolves mail.yourdomain.com to your server's IP
4. The sender connects to your server on port 25 and delivers the email
5. MXHook accepts, parses, routes, and delivers it as a webhook

Multiple Domains

MXHook supports receiving email on multiple domains. Add MX records for each domain pointing to the same server, and register each domain via the API:

curl -X POST http://localhost:8080/domains \
  -H "X-API-Key: your-api-key" \
  -d '{"name": "domain-one.com"}'

curl -X POST http://localhost:8080/domains \
  -H "X-API-Key: your-api-key" \
  -d '{"name": "domain-two.com"}'

Verification

After setting up DNS, verify the MX record is propagated:

dig MX yourdomain.com +short

Expected output:

10 mail.yourdomain.com.

Then verify the A record:

dig A mail.yourdomain.com +short

Expected output:

YOUR_SERVER_IP

Troubleshooting

MX record not resolving

• DNS propagation can take up to 48 hours. Most providers propagate within minutes.
• Verify you're editing the correct DNS zone.

Email not arriving

• Ensure port 25 (TCP) is open in your firewall and cloud provider security group.
• Many cloud providers (AWS, GCP, Azure) block inbound port 25 by default. You may need to request an exception.
• Check MXHook logs for connection attempts.

Rejected at SMTP level

• Make sure the recipient's domain is registered in MXHook via POST /domains.