Send the same message to thousands of recipients with a single API call. Define your content once, personalize it with variables, and let Postmark handle the rest.
Previously, sending bulk email through Postmark meant calling the /email endpoint repeatedly for each recipient, or packing duplicate content into every message in a /batch call. Both approaches led to bloated payloads, slower upload times, and more code to maintain — not ideal when you're sending at scale.
With the Bulk API, you define your message content (subject, HTML, text body, and attachments) once at the request level, pass a list of recipients, and Postmark compiles and delivers the individual messages. The result: dramatically smaller payloads, faster send time, and cleaner code.
With the Bulk API, you can:
All bulk sends travel through Postmark's dedicated Broadcast infrastructure, keeping your transactional and bulk traffic on separate IPs with separate reputations. This means no mixed traffic and better deliverability for both at no extra cost.
The Bulk API is available to all Postmark customers! Contact our support team to get it enabled for your account, then check out the API documentation to get started.
How does the Bulk API compare to Batch?
The Bulk API is purpose-built for sending the same message to many recipients, while the Batch API is better suited for sending different messages to different recipients in a single call. With Bulk, content is defined once and shared across all recipients; with Batch, content must be defined separately for each message. Batch API can be transactional emails but Bulk API must be broadcast. If you're sending newsletters, product announcements, policy updates, or platform notifications at scale, the Bulk API is the right tool for the job.
