Send Transactional Emails with EffiLink API

Transactional emails are system-triggered messages sent to a single recipient in response to a user action or event. Common use cases include order confirmations, password reset links, shipping notifications, account verification emails, and any other time-sensitive, personalized message that a user expects to receive. The EffiLink transactional email endpoint gives you full control over content, scheduling, tracking, and deliverability for every individual message you send.

Quick start

Send a single transactional email with a POST request to /v5/transactional/mail/sends_customised.

curl -X POST https://api.effilink.co/v5/transactional/mail/sends_customised \
  -H "ApiKey: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "subject": "Your order has shipped",
    "content": "<p>Hi Jane, your order #1234 is on its way!</p>",
    "senderMail": "no-reply@yourdomain.com",
    "senderName": "Your Store",
    "to": {
      "email": "jane.doe@example.com",
      "name": "Jane Doe"
    }
  }'

A successful response returns:

{
  "code": 200,
  "message": ""
}

Your senderMail address must be registered and verified in your EffiLink account before you can send. Unregistered senders return a 403 error.

Using templates and personalization

Instead of inlining HTML in every request, you can store reusable templates in EffiLink and reference them by name. Pass the template name in templateName and supply dynamic values through the params object using personalization tags.

curl -X POST https://api.effilink.co/v5/transactional/mail/sends_customised \
  -H "ApiKey: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "templateName": "order-shipped",
    "params": {
      "firstName": "Jane",
      "orderNumber": "1234",
      "trackingUrl": "https://track.example.com/1234"
    },
    "senderMail": "no-reply@yourdomain.com",
    "senderName": "Your Store",
    "to": {
      "email": "jane.doe@example.com",
      "name": "Jane Doe"
    }
  }'

templateName takes priority over any content field you include in the same request.
Personalization tags in your template (e.g. {{firstName}}) are replaced with the values you provide in params.
If neither content nor templateName is supplied, the request returns a 400 error.

Scheduling a send

Set sendDate to an ISO 8601 UTC timestamp to deliver the email at a specific time — up to 72 hours in the future. Leave sendDate empty (or omit it) to send immediately.

{
  "sendDate": "2024-06-15T09:00:00Z"
}

sendDate must be in valid ISO 8601 UTC format. Malformed timestamps return a 400 error. The maximum allowed scheduling window is 72 hours from the time of the request.

Attaching a file

Include a single file attachment using the attachment object. File content must be base64-encoded.

{
  "attachment": {
    "fileName": "invoice-1234.pdf",
    "fileData": "JVBERi0xLjQKJ..."
  }
}

Only one attachment is supported per transactional email request. For multiple files, consider hosting them and linking from the email body. The total email size limit over SMTP is 10 MB.

Batch sending with `messageVersions`

When you need to send up to 100 personalized versions of the same email in a single API call, use the messageVersions array. Each version can target up to 20 recipients and override the global subject, content, template, or params.

curl -X POST https://api.effilink.co/v5/transactional/mail/sends_customised \
  -H "ApiKey: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "senderMail": "no-reply@yourdomain.com",
    "senderName": "Your Store",
    "subject": "Your order update",
    "templateName": "order-update",
    "messageVersions": [
      {
        "to": [{ "email": "alice@example.com", "name": "Alice" }],
        "params": { "firstName": "Alice", "orderNumber": "1001" }
      },
      {
        "to": [{ "email": "bob@example.com", "name": "Bob" }],
        "params": { "firstName": "Bob", "orderNumber": "1002" },
        "subject": "Bob, your order update is here"
      }
    ]
  }'

Priority rules when using messageVersions:

Field	Priority
`messageVersions[].templateName`	Highest (overrides global templateName and content)
`messageVersions[].content`	High (overrides global content)
`messageVersions[].subject`	Version-level (overrides global subject)
`messageVersions[].params`	Version-level (overrides matching keys in global params)
Global `templateName` / `content`	Fallback

Each version also supports cc and bcc arrays (up to 20 addresses each). See the API reference for the full messageVersions schema.

Tracking opens and clicks

Enable engagement tracking by adding trackOpen and trackClick to your request:

{
  "trackOpen": 1,
  "trackClick": 1
}

trackOpen: 1 — EffiLink inserts a transparent tracking pixel to detect when the email is opened.
trackClick: 1 — All links in the email are rewritten through EffiLink’s click-tracking service.

To exclude a specific link from click tracking, add the ef:disable-tracking attribute to the anchor tag:

<a href="https://example.com/unsubscribe" ef:disable-tracking>Unsubscribe</a>

For more details on tracking and consuming event data via webhooks, see Email Tracking.

Common errors

Code	Cause	Resolution
`400`	Missing required parameter (`subject`, `senderMail`, `to`, and `content` or `templateName`)	Check that all required fields are present
`400`	`sendDate` format is invalid	Use ISO 8601 UTC format, e.g. `2024-06-15T09:00:00Z`
`400`	`category`, `campaign`, or `uniqueMsgID` exceeds max length	`category` and `campaign` max 100 bytes; `uniqueMsgID` max 50 bytes
`400`	`senderName` exceeds 200 bytes	Shorten the display name
`400`	Invalid `replyTo` address	Verify the reply-to email address format
`400`	No content provided	Include either `content` or `templateName`
`403`	Sender address not registered	Register and verify `senderMail` in your EffiLink dashboard
`403`	Template not found	Confirm the `templateName` exists in your account
`403`	Insufficient credits	Top up your account balance

Get Started

Authentication

Email

SMS

Contacts & Lists

Webhooks

Limits & Quotas

Send Transactional Emails with EffiLink API

Quick start

Using templates and personalization

Scheduling a send

Attaching a file

Batch sending with `messageVersions`

Tracking opens and clicks

Common errors

​Quick start

​Using templates and personalization

​Scheduling a send

​Attaching a file

​Batch sending with messageVersions

​Tracking opens and clicks

​Common errors

Quick start

Using templates and personalization

Scheduling a send

Attaching a file

Batch sending with `messageVersions`

Tracking opens and clicks

Common errors