Built-In Email

Diploi provides a lightweight SMTP relay inside every deployment so your applications can send email without provisioning an external provider. The service is intended for development and low-volume operational notifications.
The SMTP relay is included with your deployment at no additional cost.

Connection details

Connect using these values:

• Host: core.diploi
• Port: 2525
• Authentication: Not required

Note

This SMTP relay is only reachable from processes running inside your Diploi deployment network. External services cannot connect.

Example configuration

import nodemailer from "nodemailer";

const transporter = nodemailer.createTransport({
  host: "core.diploi",
  port: 2525,
});

await transporter.sendMail({
  to: "[email protected]",
  subject: "Verify your email",
  text: "Click the link in the email to verify your account.",
});

Component integration

The Supabase component automatically points its email authentication workflows at this relay, giving you out-of-the-box email confirmation flows without additional configuration.

Usage limits

Caution

The relay enforces strict rate limits to keep the service reliable for all tenants.

• Maximum 10 messages per hour
• Maximum 30 messages per day
• Contact support if you need higher throughput

Header normalization

To protect deliverability, Diploi rewrites certain email headers. These headers are stripped if present:

• from
• to
• sender
• reply-to
• return-path
• resent-from
• resent-to
• resent-sender
• bcc
• cc
• errors-to
• x-original-from
• x-envelope-from

Diploi sets the from address to your project’s default domain for every message.

Best practices

• Use the relay for development and staging workloads; production-grade email should use a dedicated provider once you outgrow the limits.
• Keep transactional content concise to avoid hitting daily limits.
• Reach out to support if you need custom limits or additional deliverability controls.