Batch Object - Collection of Email or Template Objects

Creates a Batch object for sending multiple emails or templates via the Postmark batch API. This wraps a collection of messages (either Email or Template objects) and manages the complexities of Postmark's batch API:

• Homogeneity validation: All messages must be the same type (either all Email or all Template)

• Automatic chunking: Splits large batches into API-compliant chunks of 500 messages (Postmark's limit)

• Configurable chunk size: Allows smaller chunks for testing or rate limiting

Batch API Endpoints:

• For Email messages: /email/batch

• For Template messages: /email/batchWithTemplates

Important Limitations:

• Maximum 500 messages per API call (handled automatically via chunking)

• Maximum 50 MB total payload size per chunk

• Each message still subject to individual limits (50 recipients, 10 MB)

Usage

batch(messages, chunk_size = POSTMARK_MAX_BATCH_SIZE)

Batch(messages = list(), chunk_size = 500L)

Arguments

messages

List of Email or Template objects. All must be the same class. Use lapply() or similar to create multiple messages programmatically.

chunk_size

Integer scalar. Maximum messages per API call. Default is 500 (Postmark's limit). Set lower for testing (e.g., 50) or conservative rate limiting (e.g., 100). Must be positive and not exceed 500.

See also

• https://postmarkapp.com/developer/api/email-api#send-batch-emails for Email batch API

• https://postmarkapp.com/developer/api/templates-api#send-batch-with-templates for Template batch API

• email() for single email messages

• template() for template-based messages

• send() for sending batches

Examples

if (FALSE) { # \dontrun{
# Batch of regular emails (e.g., 1000 personalized emails)
emails <- lapply(1:1000, function(i) {
  email(
    from = "sender@example.com",
    to = sprintf("user%d@example.com", i),
    subject = sprintf("Welcome User %d", i),
    html_body = sprintf("<p>Hello User %d!</p>", i)
  )
})
my_batch <- batch(messages = emails)

# Send batch
client <- client(token = "<token>", message_stream = "outbound")
result <- send(client, my_batch)

# Batch of template emails
recipients <- c("alice@example.com", "bob@example.com", "charlie@example.com")
templates <- lapply(recipients, function(email) {
  template(
    from = "notifications@example.com",
    to = email,
    id = 12345678L,
    template_model = list(
      company_name = "ACME Corp"
    )
  )
})
my_batch <- batch(messages = templates)
send(client, my_batch)
} # }