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The turboSMTP REST API lets you send email over HTTPS without an SMTP client library. Make a single HTTP POST request with a JSON body to dispatch transactional messages, notifications, or bulk campaigns from any language or platform that can speak HTTP. The API supports HTML and plain-text bodies, multiple recipients, CC and BCC, custom headers, per-message tracking IDs for webhook correlation, and attachments within the 24 MB total message limit, including encoding overhead.

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Endpoints

turboSMTP provides two send endpoints. Choose based on your data-residency requirements.
turboSMTP is an Italian company with European sending infrastructure. Use api.eu.turbo-smtp.com for the EU sending route. Review data residency for compliance considerations.
POST /mail/send requires consumerKey and consumerSecret headers with HTTP API Sending enabled. An Authorization header is ignored and cannot authenticate the request by itself. See API keys to create credentials.

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Request headers

Send these three headers with every /mail/send request.

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Request body

The request body must be a JSON object. The from and to fields are required; all other fields are optional.
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string
required
The sender’s email address. Use a verified sender domain so your messages can authenticate as your domain. You can include a display name: "Your Company <hello@your-company.com>".
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string
required
One or more recipient email addresses. Separate multiple addresses with commas. Example: "alice@example.com,bob@example.com"
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string
The subject line of the email. The API specification sets a maximum of 700 characters.
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string
The plain-text body of the email. Include this field to ensure compatibility with email clients that do not render HTML.
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string
The HTML body of the email. You can provide both content and html_content in the same request; email clients that support HTML will render html_content and fall back to content.
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string
One or more CC (carbon copy) email addresses, comma-separated.
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string
One or more BCC (blind carbon copy) email addresses, comma-separated. BCC recipients are hidden from all other recipients.
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object
Additional SMTP headers to include in the message, expressed as a JSON object. Example: {"Reply-To": "support@example.com", "X-Mailer": "MyApp/1.0"}
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string
A custom identifier included in event webhook data when provided. Use a UUID to correlate events with your application.
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string
A top-level campaign identifier used to group messages. Use this exact capitalization. Filter by it in analytics; the X-Campaign-Id header on the delivered message is internal and does not carry this value.
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array
An array of attachment objects. Each object must include name (filename), type (MIME type), and content (Base64-encoded file data). Add optional content_id for inline images. The total size of the email including all attachments must be under 24 MB. See Attachments for full details and examples.
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string
Accepted by the request schema, but /mail/send does not use it. A request that carries only mime_raw is delivered with an empty body, and the raw message’s headers and subject are discarded; when content or html_content is present, those are sent instead. To send a pre-built MIME message, use the SMTP relay.

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Example request

The following cURL command sends a basic email with both a plain-text and an HTML body.
Send an email
A successful response returns HTTP 200 with the following body:
Success response
The mid field is the turboSMTP message ID, which you can use to look up delivery status in the dashboard or via the analytics API.

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Response codes

An error response body looks like this:
Error response

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Next steps

Code Examples

Copy-paste examples for cURL, Python, Node.js, PHP, Ruby, Go, Java, and C#.

Attachments

Learn how to attach PDFs, images, and other files using Base64 encoding.