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MailStream

mailstream.app

WebAPI
Visit mailstream.app
Spec score 7.3 #18 of 28 in Direct Mail Automation Software

What it is

MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters domestically. Postcards are offered in 4×6, 6×9, and 6×11 inch sizes, while letters use HTML templates or uploaded PDFs in white #10 double-window envelopes. A browser HTML and CSS editor supports personalized designs, reusable templates, 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 expose status through the dashboard, API, or webhooks. Printing and USPS handoff are listed at 1 to 2 business days, for campaigns targeting 10 to 100,000 addresses. Integrations include Shopify, Zapier, Make, n8n, and HTTP tools. The hosted MCP server lists 27 tools. A free plan is available; paid access starts at $99/mo. Security features include TLS 1.2 or higher, AES-256 at-rest encryption, annual SOC 2 Type 2 audits, and HIPAA handling with BAAs.

Spec sheet

What it does
MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters.Read 2 Oct 2026 · mailstream.app
Product
MailStream provides a self-serve platform, REST API, and MCP server for sending physical postcards and letters.Read 3 Oct 2026 · mailstream.app
Intended users
The about page describes MailStream as physical-mail infrastructure for AI agents, agencies, SaaS teams, and business operators.Read 2 Oct 2026 · mailstream.app
Audience
MailStream describes itself as serving developers, AI agents, teams, agencies, SaaS businesses, and operators automating direct mail.Read 3 Oct 2026 · mailstream.app
Integrations
The integrations page describes Planning Center as available and lists several others, including Shopify, Zapier, Make, and n8n, as coming soon.Read 3 Oct 2026 · mailstream.app
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.Read 3 Oct 2026 · mailstream.app
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.Read 3 Oct 2026 · mailstream.app
Support
The security page says MailStream will share SOC 2 reports, complete security questionnaires, and arrange calls with its security team.Read 3 Oct 2026 · mailstream.app
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.Read 3 Oct 2026 · mailstream.app
Address checks
MailStream says addresses are CASS-verified before printing and invalid or incomplete addresses are flagged.Read 2 Oct 2026 · mailstream.app
Address validation
The service says it CASS-verifies addresses before printing and flags invalid or incomplete addresses.Read 3 Oct 2026 · mailstream.app
AI agents
The hosted MCP server offers 27 tools and lists compatibility with Claude, ChatGPT, Cursor, LangChain, AutoGen, and n8n.Read 2 Oct 2026 · mailstream.app
Automation
The REST API and MCP server support sending, tracking, address verification, and creative generation.Read 3 Oct 2026 · mailstream.app
Design
Its browser-based HTML and CSS editor supports personalized designs, reusable templates, and print proofs.Read 3 Oct 2026 · mailstream.app
Letters
Letters can be created from HTML templates or uploaded as PDFs, personalized with merge variables, and sent in #10 double-window envelopes.Read 3 Oct 2026 · mailstream.app
Personalization
The service supports variable fields such as names, offer codes, QR links, account numbers, and balances in mail designs.Read 2 Oct 2026 · mailstream.app
Postcards
Postcards are available in 4×6, 6×9, and 6×11 inch sizes, with full-bleed printing on premium stock.Read 3 Oct 2026 · mailstream.app
Printing
MailStream says it prints and hands mail to USPS within 1 to 2 business days.Read 2 Oct 2026 · mailstream.app
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.Read 3 Oct 2026 · mailstream.app
Tracking
Mail pieces use USPS Intelligent Mail barcodes, with status available through the dashboard, API, or webhooks.Read 3 Oct 2026 · mailstream.app
Webhook reliability
Webhooks use HMAC-SHA256 signatures and retry failed or timed-out deliveries up to five attempts over 24 hours.Read 2 Oct 2026 · mailstream.app

Strong points and limits

Strong points

  • REST API and MCP server
  • Variable mail personalization
  • CASS address verification
  • USPS barcode tracking
  • 1 to 2 business day handoff

Limits

  • Paid plans start at $99/mo
  • Delivery scope is domestic
  • Postcard sizes are limited
  • Free plan only

Who it suits

MailStream is aimed at developers, AI agents, agencies, SaaS teams, and operators automating direct-mail campaigns. It suits users who need programmable sending, address checks, personalization, tracking, and domestic delivery.

Verdict

MailStream combines browser design tools with API and MCP automation for physical mail. Its formats, personalization, address validation, tracking, and named integrations cover automated postcard and letter campaigns.

Where Specifiction places it

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