MailStream helps businesses send physical postcards and letters through a web platform, REST API, or MCP server. It supports campaigns aimed at 10 to 100,000 addresses, with printing and USPS handoff stated at 1 to 2 business days. Postcards come in 4×6, 6×9, and 6×11 inch sizes; letters can be created from HTML templates or uploaded PDFs and mailed in white #10 double-window envelopes. A browser-based HTML and CSS editor supports reusable templates and print proofs, while variable fields can personalize designs with details such as names, QR links, offer codes, account numbers, or balances. MailStream says it checks addresses with CASS before printing and provides USPS Intelligent Mail barcode status through its dashboard, API, or webhooks. Integrations named include Shopify, Zapier, Make, n8n, HTTP-compatible tools, and several CRM platforms. Its hosted MCP server lists 27 tools. MailStream offers a free plan and paid access from $99/mo; delivery scope is domestic.
Who it is for
MailStream suits developers, AI agents, agencies, SaaS teams, and operators automating direct mail. It may also fit healthcare clients seeking HIPAA-compliant handling and BAAs.
What is good
- Supports postcards and letters through API and web
- Personalizes mail with variable fields
- CASS address checks flag incomplete entries
- USPS tracking appears in dashboard, API, or webhooks
- Free plan available
What to know first
- Delivery scope is domestic
- Paid access starts at $99/mo
Verdict
MailStream combines physical mail production with API and MCP-based automation, address checks, and USPS tracking. The free plan offers a way to start, while paid access begins at $99/mo.
Compared on direct mail automation software
- Free plan
- Yes
- Paid from
- $99/mo
- Mail formats
- 4×6, 6×9, and 6×11 postcards; 8.5×11 letters
- Personalization level
- variable
- API access
- Yes
- CRM connections
- Planning Center, HubSpot, Salesforce, GoHighLevel, ActiveCampaign
- Address verification
- Yes
- Delivery scope
- domestic
