API email — also called an email API (application programming interface) — is a service that lets software send, track and manage emails programmatically by making HTTP requests to an email provider, instead of sending them from an email client or by talking SMTP directly. Developers use an email API to send transactional emails such as password resets, order confirmations and notifications straight from their website or application.
How an email API works
- Authenticate: your application identifies itself with an API key issued by the email provider.
- Send a request: the application makes an HTTPS request (usually to a REST endpoint) with the message data — sender, recipient, subject, HTML or text content, attachments — typically formatted as JSON.
- Get a response: the provider accepts the message, returns a status (and usually a message ID) or an error code you can handle in your code.
- Deliver and report: the provider handles the SMTP delivery, bounces and retries, then reports events such as deliveries, opens, clicks and bounces — by API calls or through webhooks that push each event to your server in real time.
Email API vs SMTP
| Email API | SMTP relay | |
|---|---|---|
| Protocol | HTTPS requests (REST, JSON) | SMTP, the standard email protocol |
| Setup | Code in your application | Server, port, username and password in your software's settings |
| Best for | Custom apps, developers, automation | Existing tools: CMS, CRM, e-commerce, ERP |
| Feedback | Structured responses, message IDs, webhooks | SMTP reply codes; events in the provider's logs |
| Speed | Fewer round trips per message | More back-and-forth per message |
Both reach the same inbox. Use SMTP when your software already supports it; choose an email API when you build your own integration. Our article SMTP relay vs email API compares them in detail.
Common email API use cases
- Transactional emails: receipts, invoices, shipping notices, password resets, one-time codes
- Account and security alerts triggered by your application
- Personalized notifications and reports generated from your own data
- Syncing events and statistics back into your CRM or back office
The Mailpro email API
The Mailpro Email API lets your application send campaigns and transactional emails, manage address books, templates and senders, and retrieve statistics (opens, clicks, countries, bounces). Mailpro also offers a CRM API and an SMS API. According to the Mailpro API page, the APIs provide:
- REST and JSON, with XML also available on the Email API, and standard HTTP verbs and status codes.
- Authentication by API key, bearer token or OAuth 2.0 (PKCE) for third-party tools, over HTTPS. You find your API key in your Mailpro account under Settings, API Settings.
- Delivery tracking: every transactional email returns an identifier you can use to query its status (delivered, deferred, bounced).
- Signed webhooks for events such as email delivered, bounce, open and click, pushed to your URL as JSON, signed with HMAC-SHA256 and retried automatically.
- Rate limit of 500 requests per minute per account, with a 429 response and Retry-After header beyond that.
Endpoints are documented on the Mailpro developer portal, and an open-source starter with examples in Node.js, Python, PHP, C# and Java is on GitHub. For setup questions, see the FAQ API email and how APIs work, or Mailpro's API solutions. Deciding between a raw email API and a managed platform? See our guide to the best Amazon SES alternatives.
Mailpro and email API
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