# Transactional Emails (/concepts/transactional-emails)

A transactional email is one your application sends straight through the API — the one-to-one messages a user expects immediately, like password resets, order confirmations, and account notifications.

## Sending with attachments

Attachments are supported on transactional sends. The default limits allow up to 10 attachments on a single email, with their combined size capped at 10MB. Encode each file as base64 and pass it in the `attachments` array of your request to the [/v1/email/send](/api-reference/public-api/sendEmail) endpoint.

The message as a whole may not exceed 40 MB.

## Sending from a template

Transactional emails can also reference a [template](/concepts/templates) built in the dashboard. That way one design serves many sends, and each email is still personalized with the recipient's contact data.

## What's next

<Cards>
  <Card title="Send Email API" href="/api-reference/public-api/sendEmail">
    Complete reference for `POST /v1/send`.
  </Card>

  <Card title="Templates" href="/concepts/templates">
    Build email designs you can reuse.
  </Card>

  <Card title="API keys" href="/guides/api-keys">
    How `sk_*` and `pk_*` keys authenticate your requests.
  </Card>

  <Card title="Webhooks" href="/guides/webhooks">
    Follow deliveries, opens, clicks, and bounces for every send.
  </Card>
</Cards>