Introduction

Postmark helps deliver and track application email. In a nutshell, the service replaces SMTP (or Sendmail) with a far more reliable, scalable and care-free environment. In addition, you can track statistics such as number of emails sent or processed, opens, bounces and spam complaints.

Things you should know

• Postmark separates emails by Message Streams. Transactional Message Streams are for one to one emails triggered by a user action like a welcome email, password reset, or order confirmation. Newsletters, announcements, or any other bulk email can be sent through Broadcast Message Streams. If you’re uncertain if your email qualifies as Transactional or Broadcast, you can always contact support and we’ll review your usage.
• A confirmed email address is required to start sending. Before you can start sending emails, you will need to verify the email address you send from in our Signatures section.
• Maximum email size is 10 MB. This includes email content, headers, and attachments. You will receive an error if your emails are too large.
• Postmark will only accept attachments with specific file types, so please review our list of accepted file types. We also support inline image embedding.
• The maximum number of recipients for each email is 50, including all To, CC, and BCC recipients. Each recipient counts as a single Postmark email or a single Postmark credit for older accounts.

AI tooling

If you're using AI coding assistants in your development workflow, we've made it easier for them to help you work with Postmark. Our llms.txt file gives tools like ChatGPT and Claude structured information about our API and features. Just paste the link when you need context about Postmark. For deeper integration, the Postmark MCP server connects directly to compatible AI tools, letting them search messages, check delivery stats, and work with templates. You can also use the Postmark CLI to interact with your Postmark account from the command line, whether you're testing locally or automating tasks.

• Postmark MCP server
• Postmark llms.txt
• Postmark CLI

Get started