Batch Transactional Email Send — Up to 100 Versions

Overview

Send up to 100 personalized email versions in a single API call using the messageVersions array. Each version can target up to 20 recipients and independently override the top-level subject, content, template, and personalization parameters. This is the most efficient way to dispatch a batch of individually tailored transactional messages without making one request per recipient. This uses the same endpoint as single transactional sends, with the addition of the messageVersions field. Base URL: https://api.effilink.co Endpoint: POST /v5/transactional/mail/sends_customised Authentication: ApiKey header

Content Priority Order

When multiple content sources are provided, the following priority applies (highest to lowest):

messageVersions[].templateName
messageVersions[].content
Top-level templateName
Top-level content

Request Parameters

All single send parameters are supported at the top level and serve as defaults across all versions. The messageVersions array is required for batch sends.

string

Default email subject line, used for any version that does not define its own subject.

string

Default HTML email body content. Used for versions that do not specify content or templateName. Required if no top-level templateName is set and no version provides its own content source.

string

Default saved template name. Used for versions that do not specify their own templateName or content.

object

Default key-value personalization tags applied to all versions. Version-level params override these values when the same key is present.

{ "brand": "Your Store", "supportEmail": "help@yourdomain.com" }

string

required

Verified sender email address. Applies to all versions.

string

Sender display name. Maximum 200 bytes. Applies to all versions.

string

Reply-to email address. Applies to all versions.

string

Scheduled send time in ISO 8601 UTC format (e.g. 2024-03-10T12:00:00Z). Up to 72 hours in advance. Omit to send immediately.

integer

Set to 1 to enable open tracking across all versions.

integer

Set to 1 to enable click tracking across all versions.

string

Email category label. Maximum 100 bytes, alphanumeric only.

string

Campaign name for analytics grouping. Maximum 100 bytes, alphanumeric only.

string

A unique message identifier for tracking and deduplication purposes. Maximum 50 bytes.

object

A single file to attach to all emails in the batch. Only one attachment is supported per request.

Show attachment fields

string

required

The filename of the attachment, including its extension (e.g. invoice.pdf).

string

required

Base64-encoded content of the file to attach.

boolean

Set to true to validate and process the request without delivering any emails.

array

required

Array of up to 100 individual email versions. Each version inherits top-level values and may override them selectively.

Show messageVersions[] fields

array

required

List of primary recipients for this version. Maximum 20 recipients.Each item: { "email": "string (required)", "name": "string (optional)" }

array

List of CC recipients for this version. Maximum 20 recipients.Each item: { "email": "string (required)", "name": "string (optional)" }

array

List of BCC recipients for this version. Maximum 20 recipients.Each item: { "email": "string (required)", "name": "string (optional)" }

string

Version-level subject line. Overrides the top-level subject for this version only.

string

Version-level HTML email body. Overrides the top-level content for this version (unless a version-level templateName is also set).

string

Version-level template name. Takes highest priority — overrides both version-level content and all top-level content sources.

object

Version-level personalization tags. These override any matching keys from the top-level params for this version only.

{ "name": "Alice", "orderId": "ORD-001", "status": "Shipped" }

Response Fields

integer

200 on success. See the error codes table for failure values.

string

Empty string ("") on success. Contains an error description on failure.

Error Codes

Code	Cause
`400`	Missing required parameter; `messageVersions` exceeds 100 entries; a version’s `to`, `cc`, or `bcc` array exceeds 20 recipients; invalid `sendDate` format; `category`, `campaign`, or `uniqueMsgID` too long; invalid recipient address; sender name too long; invalid reply-to address; missing content
`403`	Sender address not registered; template not found; insufficient account credits

Example

Request

curl --request POST \
  --url https://api.effilink.co/v5/transactional/mail/sends_customised \
  --header 'Content-Type: application/json' \
  --header 'ApiKey: YOUR_API_KEY' \
  --data '{
    "subject": "Order update for {{orderId}}",
    "content": "<p>Hello {{name}},</p><p>Your order {{orderId}} status: {{status}}</p>",
    "senderMail": "noreply@yourdomain.com",
    "trackOpen": 1,
    "messageVersions": [
      {
        "to": [{"email": "alice@example.com", "name": "Alice"}],
        "params": {"name": "Alice", "orderId": "ORD-001", "status": "Shipped"}
      },
      {
        "to": [{"email": "bob@example.com", "name": "Bob"}],
        "params": {"name": "Bob", "orderId": "ORD-002", "status": "Processing"}
      }
    ]
  }'

Response

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

Transactional Email

Campaign Email

SMS

Contacts & Lists

Webhooks

Authentication

Batch Transactional Email Send — Up to 100 Versions

Overview

Content Priority Order

Request Parameters

Response Fields

Error Codes

Example

Request

Response

​Overview

​Content Priority Order

​Request Parameters

​Response Fields

​Error Codes

​Example

​Request

​Response

Overview

Content Priority Order

Request Parameters

Response Fields

Error Codes

Example

Request

Response