# Email Configuration in the Next.js Supabase SaaS Starter Kit > Configure Nodemailer (SMTP) or Resend to send transactional emails from your Next.js Supabase application. Learn the difference between MakerKit emails and Supabase Auth emails. *Canonical: https://makerkit.dev/docs/next-supabase-turbo/emails/email-configuration* --- MakerKit uses the `@kit/mailers` package to send transactional emails like team invitations and account notifications. You can choose between Nodemailer (any SMTP provider) or Resend (HTTP API). ## MakerKit vs Supabase Auth Emails Before configuring your email provider, understand the two email systems in your application: | Email Type | Purpose | Configuration | Examples | |------------|---------|---------------|----------| | **MakerKit Emails** | Application transactional emails | Environment variables | Team invitations, account deletion, OTP codes | | **Supabase Auth Emails** | Authentication flows | Supabase Dashboard | Email verification, password reset, magic links | This guide covers MakerKit email configuration. For Supabase Auth emails, see the [Authentication Emails](/docs/next-supabase-turbo/authentication-emails) guide. ## Choosing a Mailer Provider MakerKit supports two mailer implementations: ### Nodemailer (Default) Best for: Most production deployments using any SMTP provider (SendGrid, Mailgun, Amazon SES, etc.) - Works with any SMTP server - Requires Node.js runtime (not compatible with Edge) - Full control over SMTP configuration ### Resend Best for: Edge runtime deployments, simpler setup, or if you're already using Resend - HTTP-based API (Edge compatible) - No SMTP configuration needed - Requires Resend account and API key ## Configuring Nodemailer Nodemailer is the default provider. Set these environment variables in `apps/web/.env`: ```bash MAILER_PROVIDER=nodemailer # SMTP Configuration EMAIL_HOST=smtp.your-provider.com EMAIL_PORT=587 EMAIL_USER=your-smtp-username EMAIL_PASSWORD=your-smtp-password EMAIL_TLS=true EMAIL_SENDER=YourApp ``` ### Environment Variables Explained | Variable | Description | Example | |----------|-------------|---------| | `EMAIL_HOST` | SMTP server hostname | `smtp.sendgrid.net`, `email-smtp.us-east-1.amazonaws.com` | | `EMAIL_PORT` | SMTP port (587 for STARTTLS, 465 for SSL) | `587` | | `EMAIL_USER` | SMTP authentication username | Varies by provider | | `EMAIL_PASSWORD` | SMTP authentication password or API key | Varies by provider | | `EMAIL_TLS` | Use secure connection (`true` for SSL on port 465, `false` for STARTTLS on port 587) | `true` | | `EMAIL_SENDER` | Sender name and email address | `MyApp ` | **Note**: `EMAIL_TLS` maps to Nodemailer's `secure` option. When `true`, the connection uses SSL/TLS from the start (typically port 465). When `false`, the connection starts unencrypted and upgrades via STARTTLS (typically port 587). Most modern providers use port 587 with `EMAIL_TLS=false`. ### Provider-Specific Configuration #### SendGrid ```bash EMAIL_HOST=smtp.sendgrid.net EMAIL_PORT=587 EMAIL_USER=apikey EMAIL_PASSWORD=SG.your-api-key-here EMAIL_TLS=true EMAIL_SENDER=YourApp ``` #### Amazon SES ```bash EMAIL_HOST=email-smtp.us-east-1.amazonaws.com EMAIL_PORT=587 EMAIL_USER=your-ses-smtp-username EMAIL_PASSWORD=your-ses-smtp-password EMAIL_TLS=true EMAIL_SENDER=YourApp ``` #### Mailgun ```bash EMAIL_HOST=smtp.mailgun.org EMAIL_PORT=587 EMAIL_USER=postmaster@your-domain.mailgun.org EMAIL_PASSWORD=your-mailgun-password EMAIL_TLS=true EMAIL_SENDER=YourApp ``` ### EMAIL_SENDER Format The `EMAIL_SENDER` variable accepts two formats: ```bash # With display name (recommended) EMAIL_SENDER=YourApp # Email only EMAIL_SENDER=hello@yourapp.com ``` {% alert type="warn" title="Verify Your Sender Domain" %} Most email providers require you to verify your sending domain before emails will be delivered. Check your provider's documentation for domain verification instructions. {% /alert %} ## Configuring Resend To use Resend instead of Nodemailer: ```bash MAILER_PROVIDER=resend RESEND_API_KEY=re_your-api-key EMAIL_SENDER=YourApp ``` ### Getting a Resend API Key 1. Create an account at [resend.com](https://resend.com) 2. Add and verify your sending domain 3. Generate an API key from the dashboard 4. Add the key to your environment variables {% alert type="default" title="Edge Runtime Compatible" %} Resend uses HTTP requests instead of SMTP, making it compatible with Vercel Edge Functions and Cloudflare Workers. If you deploy to edge runtimes, Resend is the recommended choice. {% /alert %} ## Verifying Your Configuration After configuring your email provider, test it by triggering an email in your application: 1. Start your development server: `pnpm dev` 2. Sign up a new user and invite them to a team 3. Check that the invitation email arrives For local development, emails are captured by Mailpit at [http://localhost:54324](http://localhost:54324). See the [Local Development](/docs/next-supabase-turbo/emails/inbucket) guide for details. ## Common Configuration Errors ### Connection Timeout If emails fail with connection timeout errors: - Verify `EMAIL_HOST` and `EMAIL_PORT` are correct - Check if your hosting provider blocks outbound SMTP (port 25, 465, or 587) - Some providers like Vercel block raw SMTP; use Resend instead ### Authentication Failed If you see authentication errors: - Double-check `EMAIL_USER` and `EMAIL_PASSWORD` - Some providers use API keys as passwords (e.g., SendGrid uses `apikey` as username) - Ensure your credentials have sending permissions ### Emails Not Delivered If emails send but don't arrive: - Verify your sender domain is authenticated (SPF, DKIM, DMARC) - Check the spam folder - Review your email provider's delivery logs - Ensure `EMAIL_SENDER` uses a verified email address ## Next Steps - [Send your first email](/docs/next-supabase-turbo/sending-emails) using the mailer API - [Create custom email templates](/docs/next-supabase-turbo/email-templates) with React Email - [Configure Supabase Auth emails](/docs/next-supabase-turbo/authentication-emails) for verification flows