Postgate AI - Microsoft Exchange MCP Server

For developers & admins

Microsoft Exchange MCP server - on-premises and hybrid.

Postgate AI exposes Exchange mailboxes as an MCP server: 70+ tools over SSE and Streamable HTTP, OAuth 2.0/PKCE, delegated per-user permissions. Connected via EWS - for Exchange Server on-premises and hybrid environments, hosted in Germany.

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Architecture

The technology in six points

The MCP standard

Model Context Protocol - the open standard through which AI assistants access external systems. Postgate AI exposes Microsoft Exchange as an MCP server: for Claude, ChatGPT, Perplexity and any other MCP-capable client.

Transports: SSE & Streamable HTTP

Both MCP transports are supported - compatible with desktop clients, mobile apps and agent platforms. TLS on every route.

OAuth 2.0 / PKCE

Verified identity instead of trust-based headers: clients authenticate via OAuth 2.0 with PKCE, self-service onboarding via Microsoft sign-in or a one-time code from the portal.

Per-user vault

Exchange credentials are stored RSA-4096-encrypted per user in a vault in Germany. Delegated access with existing Exchange permissions - no service account, no application impersonation.

Connected via EWS

Exchange Server SE, 2019 and 2016 via EWS (Exchange Web Services) - including hybrid environments. No cloud mailbox required.

70+ tools

Mail, calendar, contacts, tasks, folders, attachments (incl. PDF/DOCX/XLSX extraction), threads, global address list, free/busy times and semantic search - the entire mailbox as a toolbox.

Integration

One MCP server, three ways to use it

AI assistants

Claude, ChatGPT and Perplexity - desktop and mobile. Gemini via Gemini Enterprise or the Gemini CLI.

Agent platforms

Microsoft Copilot Studio plugs Postgate AI in as an MCP tool - your Copilot agent works with on-premises mailboxes. More platforms like n8n are in preparation.

Your own agents

Any MCP-capable runtime can use the tools - from a Python script to a full agent platform.

Step-by-step guides: Claude, ChatGPT, Gemini, Perplexity →

Landscape

Microsoft Exchange MCP servers compared

Open-source MCP servers (self-hosted)

Stdio servers for EWS exist as open source - typically one mailbox per instance, credentials in environment variables, operation and updates on your own. Fine for a single user, laborious as a company solution.

Microsoft MCP Server (Graph)

Microsoft's own MCP server works through Microsoft Graph and covers cloud-only scenarios - it cannot reach mailboxes on an Exchange Server on-premises.

Postgate AI

Hosted multi-user MCP server for Exchange on-premises and hybrid: OAuth 2.0/PKCE, per-user vault, central administration in the portal - set up once, for all employees.

FAQ

Frequently asked questions

What is an MCP server for Microsoft Exchange?

A server that makes Exchange mailboxes accessible to AI assistants via the Model Context Protocol (MCP): emails, calendar, contacts and tasks as standardized tools that Claude, ChatGPT or your own agents can call - with the permissions of the respective user.

Does the MCP server work with Exchange on-premises?

Yes - that is the core: connection via EWS for Microsoft Exchange Server SE, 2019 and 2016, including hybrid environments. As a hosted solution, with no installation on clients.

Can I use the MCP server in Copilot Studio or n8n?

Microsoft Copilot Studio: yes. Postgate AI is added there as an MCP tool (Streamable HTTP, OAuth 2.0 with dynamic discovery) - your Copilot agent accesses on-premises mailboxes, each user with their own Exchange permissions. More platforms like n8n are in preparation - talk to us.

How do users authenticate?

Clients via OAuth 2.0 with PKCE; the user’s Exchange credentials are stored encrypted in the per-user vault. Every access is delegated, using the existing Exchange permissions of the respective user.

How is Postgate AI different from open-source MCP servers for EWS?

Open-source servers usually run as a stdio process for a single mailbox, with credentials in environment variables and self-managed operation. Postgate AI is a hosted multi-user MCP server: OAuth 2.0/PKCE, an RSA-4096 vault per user, delegated permissions and central administration in the portal - with no servers to run yourself.

Exchange as an MCP server - testable in minutes.

7 days free with your own mailbox: connect your EWS URL, pair a client, use the tools.

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