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MailStream
What it is
MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters. Postcards come in 4×6, 6×9, and 6×11 inch sizes, while letters use HTML templates or uploaded PDFs in white #10 double-window envelopes. Its browser editor supports HTML and CSS designs, reusable templates, personalization, and print proofs. Variable fields can add names, offer codes, QR links, account numbers, and balances. MailStream says it CASS-verifies addresses before printing and flags invalid or incomplete entries. USPS Intelligent Mail barcodes provide status through the dashboard, API, or webhooks. The company says printing and USPS handoff take 1 to 2 business days, with campaigns for 10 to 100,000 addresses. Named integrations include Shopify, Zapier, Make, and n8n, plus HTTP-compatible tools. The hosted MCP server lists 27 tools and compatibility with several AI-agent platforms. Paid access starts at $99/mo, and delivery is domestic.
For and against
For
- Postcards and letters supported
- Variable-field personalization
- CASS address verification
- USPS barcode tracking
- REST API and MCP server
Against
- Domestic delivery only
- Paid access starts at $99/mo
- Printing and USPS handoff take 1 to 2 business days
- No broader delivery scope is listed
The verdict
MailStream combines design tools with programmable sending, validation, and tracking for physical mail. Its domestic scope and starting price should be weighed against the automation features.
Who it suits
MailStream is aimed at developers, AI agents, agencies, SaaS teams, and operators automating direct mail. It fits teams needing API-based sending, address checks, personalization, and tracking.
On the record
- Address checks
- MailStream says addresses are CASS-verified before printing and invalid or incomplete addresses are flagged.mailstream.app · read 2 Oct 2026
- Address validation
- The service says it CASS-verifies addresses before printing and flags invalid or incomplete addresses.mailstream.app · read 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 · read 2 Oct 2026
- Audience
- MailStream describes itself as serving developers, AI agents, teams, agencies, SaaS businesses, and operators automating direct mail.mailstream.app · read 3 Oct 2026
- Automation
- The REST API and MCP server support sending, tracking, address verification, and creative generation.mailstream.app · read 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 · read 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 · read 3 Oct 2026
- Design
- Its browser-based HTML and CSS editor supports personalized designs, reusable templates, and print proofs.mailstream.app · read 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 · read 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 · read 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 · read 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 · read 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 · read 3 Oct 2026
- Printing
- MailStream says it prints and hands mail to USPS within 1 to 2 business days.mailstream.app · read 2 Oct 2026
- Product
- MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters.mailstream.app · read 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 · read 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 · read 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 · read 3 Oct 2026
