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Shipfastai sends transactional emails through Resend — a developer-focused email API. Emails are optional: if you leave RESEND_API_KEY unset, the application starts normally and logs a warning instead of sending. This makes local development easier because you can register and verify accounts without a real email provider.

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Resend setup

To enable email sending, create a free Resend account at resend.com, then add your API key and sender address to .env:
.env
Resend’s free tier allows 3,000 emails per month and up to 100 emails per day. This is more than enough for development and early-stage production use.

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Email types sent

Shipfastai sends three types of transactional emails automatically: The FRONTEND_URL variable controls the base URL used in all email links. Make sure it matches your deployed frontend address in production.

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Customizing email templates

Email templates are defined in backend/app/core/email.py as inline HTML strings inside three methods on the EmailService class: To customize a template, open backend/app/core/email.py and edit the html variable inside the corresponding method. The templates are plain HTML strings — you can replace them with any HTML you like, including full branded designs. For example, to change the verification email subject line:
backend/app/core/email.py
If you want to use a templating library like Jinja2, install it and render the template before passing the resulting HTML string to self._send.

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Testing locally

You have two options for testing email flows during local development: Option 1: Leave RESEND_API_KEY empty (recommended) When RESEND_API_KEY is not set, the EmailService logs the would-be email to the console instead of sending it. You can still test the full registration flow — check the backend logs to see the verification token URL.
Option 2: Use a Resend test API key Resend supports sending emails to your own verified address using a real API key in test mode. Add your re_ key to .env and set FROM_EMAIL to your verified sender.
.env