# Send emails using Customer.io with SMTP

### Prerequisites

Before you start, you'll need:

- A Resend [API key](/guides/get-started-create-an-api-key)
- A [verified domain](/guides/get-started-add-a-domain)

## Guide

::::steps
:::step{title="Get the Resend SMTP credentials"}
When configuring your SMTP integration, you'll need to use the following credentials:

- **Host**: `smtp.resend.com`
- **Port**: `465`
- **Username**: `resend`
- **Password**: `YOUR_API_KEY`
:::

:::step{title="Integrate with Customer.io SMTP"}
After logging into your [Customer.io](https://customer.io) account, you'll need to enable the SMTP integration.

1. Go to **Settings** > **Workspace Settings**.

![Customer.io SMTP - Workspace Settings](../img/site-assets/mintcdn.com/resend/ABWmVTZIHGIFNTFD/images/customer-io-smtp-1-1ofq1kf.png)

2. Go to the Messaging tab and select **Email**.

![Customer.io SMTP - Email](../img/site-assets/mintcdn.com/resend/ABWmVTZIHGIFNTFD/images/customer-io-smtp-2-1u2yhga.png)

3. Select the **Custom SMTP** tab and click **Add Custom SMTP Server**.

![Customer.io SMTP - Add Custom SMTP Server](../img/site-assets/mintcdn.com/resend/ABWmVTZIHGIFNTFD/images/customer-io-smtp-3-18dnho.png)

4. Select **Other SMTP** and click **Continue to set up**.

![Customer.io SMTP - Other SMTP](../img/site-assets/mintcdn.com/resend/ABWmVTZIHGIFNTFD/images/customer-io-smtp-4-j4ai8o.png)

5. Copy-and-paste the SMTP credentials from Resend to Customer.io.

![Customer.io SMTP integration](../img/site-assets/mintcdn.com/resend/ABWmVTZIHGIFNTFD/images/customer-io-smtp-5-1ynumdx.png)
:::
::::

## Related pages

- [Send emails with SMTP](./get-started-send-with-smtp.md)
- [Send Auth0 transactional emails with Resend](./get-started-send-with-auth0.md)
- [Send emails using Django with SMTP](./get-started-send-with-django-smtp.md)
- [Send emails using Laravel with SMTP](./get-started-send-with-laravel-smtp.md)
- [Send emails using Liferay with SMTP](./get-started-send-with-liferay-smtp.md)
- [Send emails using Nodemailer with SMTP](./get-started-send-with-nodemailer-smtp.md)
- [Send emails using PHPMailer with SMTP](./get-started-send-with-phpmailer-smtp.md)
- [Send emails using Rails with SMTP](./get-started-send-with-rails-smtp.md)
- [Send emails using Retool with SMTP](./get-started-send-with-retool-smtp.md)
- [Send emails using Supabase with SMTP](./get-started-send-with-supabase-smtp.md)

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