MailStream
MailStream is a service for creating and sending physical postcards and letters through a web platform, REST API, or MCP server.
What MailStream is
MailStream is a service for creating and sending physical postcards and letters through a web platform, REST API, or MCP server. Postcards come in 4×6, 6×9, and 6×11 inch sizes; letters can be made from HTML templates or uploaded PDFs and mailed in white #10 double-window envelopes. A browser editor supports HTML and CSS designs, reusable templates, and print proofs. Variable fields can personalize mail with details such as names, offer codes, QR links, account numbers, or balances. MailStream says it checks addresses before printing and flags invalid or incomplete entries. USPS Intelligent Mail barcodes provide status through its dashboard, API, or webhooks. Printing and handoff to USPS are listed at 1 to 2 business days, with campaigns aimed at 10 to 100,000 addresses. Integrations include Shopify, Zapier, Make, n8n, and HTTP-compatible tools. The hosted MCP server lists 27 tools. MailStream offers a free plan, with paid access from $99/mo, and domestic delivery.
Good
- Web platform, REST API, and MCP server are available.
- Postcards and letters support variable personalization.
- Address checks flag invalid or incomplete entries.
- Tracking status is available in dashboard, API, or webhooks.
- Free plan is available; paid access starts at $99/mo.
Watch out
- Delivery scope is domestic only.
- Paid access starts at $99/mo.
- Mail is handed to USPS in 1 to 2 business days.
Who it suits
MailStream suits developers, AI agents, agencies, SaaS teams, and business operators automating direct-mail campaigns. Its API, MCP server, personalization, and tracking options also fit teams that want to connect mail workflows to other tools.
Verdict
MailStream brings physical mail creation, address checks, and tracking into web and API-based workflows. Its free plan and range of integrations may suit teams exploring automated direct mail, while the listed paid starting price and domestic-only scope are worth noting.
The facts
Each one read from MailStream's own pages, with the date it was checked.
What it does
- Address checks
- MailStream says addresses are CASS-verified before printing and invalid or incomplete addresses are flagged.checked 2 Oct 2026
- Address validation
- The service says it CASS-verifies addresses before printing and flags invalid or incomplete addresses.checked 3 Oct 2026
- AI agents
- The hosted MCP server offers 27 tools and lists compatibility with Claude, ChatGPT, Cursor, LangChain, AutoGen, and n8n.checked 2 Oct 2026
- Audience
- MailStream describes itself as serving developers, AI agents, teams, agencies, SaaS businesses, and operators automating direct mail.checked 3 Oct 2026
- Automation
- The REST API and MCP server support sending, tracking, address verification, and creative generation.checked 3 Oct 2026
- Compliance
- The company describes annual SOC 2 Type 2 audits, HIPAA-compliant handling and BAAs for healthcare clients, and support for CCPA and GDPR requirements.checked 3 Oct 2026
- Design
- Its browser-based HTML and CSS editor supports personalized designs, reusable templates, and print proofs.checked 3 Oct 2026
- Integrations
- The integrations page describes Planning Center as available and lists several others, including Shopify, Zapier, Make, and n8n, as coming soon.checked 3 Oct 2026
- Intended users
- The about page describes MailStream as physical-mail infrastructure for AI agents, agencies, SaaS teams, and business operators.checked 2 Oct 2026
- Letters
- Letters can be created from HTML templates or uploaded as PDFs, personalized with merge variables, and sent in #10 double-window envelopes.checked 3 Oct 2026
- Personalization
- The service supports variable fields such as names, offer codes, QR links, account numbers, and balances in mail designs.checked 2 Oct 2026
- Postcards
- Postcards are available in 4×6, 6×9, and 6×11 inch sizes, with full-bleed printing on premium stock.checked 3 Oct 2026
- Printing
- MailStream says it prints and hands mail to USPS within 1 to 2 business days.checked 2 Oct 2026
- Product
- MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters.checked 3 Oct 2026
- Scale and turnaround
- The company says campaigns can target 10 to 100,000 addresses and that mail is printed in 1 to 2 business days.checked 3 Oct 2026
- Security
- The security page states that API traffic uses TLS 1.2+, customer data and artwork use AES-256 encryption at rest, and PII is access-controlled and purged on set retention schedules.checked 3 Oct 2026
- Support
- The security page says MailStream will share SOC 2 reports, complete security questionnaires, and arrange calls with its security team.checked 3 Oct 2026
- Tracking
- Mail pieces use USPS Intelligent Mail barcodes, with status available through the dashboard, API, or webhooks.checked 3 Oct 2026
- Webhook reliability
- Webhooks use HMAC-SHA256 signatures and retry failed or timed-out deliveries up to five attempts over 24 hours.checked 2 Oct 2026
- What it does
- MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters.checked 2 Oct 2026
The company
- Company
- The About page names Jake Fassnacht, Jeff Kingsford, and Marton Gergely as co-founders and says Jeff founded an online printing and marketing company that operated from 1998 to 2018.checked 3 Oct 2026
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