Freedom251 › Direct Mail Automation Software

MailStream

Free plan APIWeb

What MailStream is

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 suits

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 it does well

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

Limits

The free plan is available; paid access starts at $99/mo. MailStream lists domestic delivery, and says printing and USPS handoff take 1 to 2 business days.

Getting started

Open https://mailstream.app/.
Choose the web platform, REST API, or hosted MCP server.
Use the browser editor to create a design or reusable template.
Prepare postcard artwork or an HTML letter template or PDF.
Add recipient addresses and any variable personalization fields.
Send a campaign and follow status in the dashboard, API, or webhooks.

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.

Questions

Does MailStream have a free plan?

Yes. MailStream has a free plan, with paid access from $99/mo.

Which formats can it mail?

It offers 4×6, 6×9, and 6×11 inch postcards, plus 8.5×11 letters. Letters can be generated from HTML templates or uploaded PDFs.

Which platforms does MailStream support?

Its listed platforms are web and API. It also provides a hosted MCP server.

Which services can connect to MailStream?

Named integrations include Shopify, Zapier, Make, and n8n, as well as tools that speak HTTP. Listed CRM connections include Planning Center, HubSpot, Salesforce, GoHighLevel, and ActiveCampaign.

Does MailStream verify addresses and track mail?

MailStream says it CASS-verifies addresses before printing and tracks mail with USPS Intelligent Mail barcodes. Status is available through its dashboard, API, or webhooks.

Who founded MailStream?

The About page names Jake Fassnacht, Jeff Kingsford, and Marton Gergely as co-founders.

Facts from MailStream's own pages

Address checks: MailStream says addresses are CASS-verified before printing and invalid or incomplete addresses are flagged. · mailstream.app, 2 Oct 2026
Address validation: The service says it CASS-verifies addresses before printing and flags invalid or incomplete addresses. · mailstream.app, 3 Oct 2026
AI agents: The hosted MCP server offers 27 tools and lists compatibility with Claude, ChatGPT, Cursor, LangChain, AutoGen, and n8n. · mailstream.app, 2 Oct 2026
Audience: MailStream describes itself as serving developers, AI agents, teams, agencies, SaaS businesses, and operators automating direct mail. · mailstream.app, 3 Oct 2026
Automation: The REST API and MCP server support sending, tracking, address verification, and creative generation. · mailstream.app, 3 Oct 2026
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. · mailstream.app, 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. · mailstream.app, 3 Oct 2026
Design: Its browser-based HTML and CSS editor supports personalized designs, reusable templates, and print proofs. · mailstream.app, 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. · mailstream.app, 3 Oct 2026
Intended users: The about page describes MailStream as physical-mail infrastructure for AI agents, agencies, SaaS teams, and business operators. · mailstream.app, 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. · mailstream.app, 3 Oct 2026
Personalization: The service supports variable fields such as names, offer codes, QR links, account numbers, and balances in mail designs. · mailstream.app, 2 Oct 2026
Postcards: Postcards are available in 4×6, 6×9, and 6×11 inch sizes, with full-bleed printing on premium stock. · mailstream.app, 3 Oct 2026
Printing: MailStream says it prints and hands mail to USPS within 1 to 2 business days. · mailstream.app, 2 Oct 2026
Product: MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters. · mailstream.app, 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. · mailstream.app, 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. · mailstream.app, 3 Oct 2026
Support: The security page says MailStream will share SOC 2 reports, complete security questionnaires, and arrange calls with its security team. · mailstream.app, 3 Oct 2026
Tracking: Mail pieces use USPS Intelligent Mail barcodes, with status available through the dashboard, API, or webhooks. · mailstream.app, 3 Oct 2026
Webhook reliability: Webhooks use HMAC-SHA256 signatures and retry failed or timed-out deliveries up to five attempts over 24 hours. · mailstream.app, 2 Oct 2026
What it does: MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters. · mailstream.app, 2 Oct 2026

Where MailStream stands on Freedom251

Direct Mail Automation Software#8 of 28