MCP server for Microsoft Exchange Server SE - on-prem (EWS) & hybrid.
Postgate AI exposes Exchange mailboxes as an MCP server, with more than 90 tools over Streamable HTTP, OAuth 2.0/PKCE and delegated per-user permissions. Mailboxes in your own network are connected via EWS, for Exchange Server Subscription Edition (SE) plus Exchange 2019 and 2016. Mailboxes in Exchange Online are reached via Microsoft Graph. Either managed by us in Germany or self-hosted as a license.
The technology in seven points
The MCP standard
Model Context Protocol is the open standard that AI assistants use to reach external systems. Postgate AI exposes Microsoft Exchange as an MCP server for Claude, ChatGPT, Perplexity, Mistral Vibe and any other MCP-capable client. We support the 28 July 2026 revision in full. Older clients keep working exactly as before, so there is nothing for you to change.
Transport: Streamable HTTP (28 July 2026 revision)
We implement the MCP revision of 28 July 2026 on the server side, with exactly one endpoint: /mcp. The new revision drops three things, and all three used to cost time: the session id, the handshake before the first tool call, and the permanently open stream per client. Every request now stands on its own. Self-hosted that means several nodes behind a plain load balancer, no session affinity, and one node more as soon as load grows. A restart no longer cuts anyone off. TLS on every route, and no client needs Server-Sent Events any more.
Sign-in: OAuth 2.0/PKCE, Entra ID or AD FS
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. Out of the box the sign-in runs through Microsoft Entra ID, which also fits a hybrid setup. If you want no cloud sign-in at all, point us at your own AD FS as the issuer - we then validate tokens from your own house. Mailbox access runs natively over the Windows sign-in (NTLM) or, once Exchange trusts your own issuer, over modern auth with a per-user token, with no domain password in the vault.
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 and Microsoft Graph
Mailboxes on an Exchange Server in your own network are connected via EWS, for Exchange Server SE, 2019 and 2016. Mailboxes in Exchange Online are reached via Microsoft Graph. Both run side by side in the same setup, and every organization sets for itself which one applies. A cloud mailbox is not a requirement.
Several nodes behind one load balancer
The current MCP revision works without session affinity. Several instances can therefore run side by side, and each request goes wherever there is room. When the number of users grows, you add another node.
90+ 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.
One MCP server, three ways to use it
AI assistants
Claude, ChatGPT, Perplexity and Mistral Vibe - desktop and mobile. Gemini via Gemini Enterprise or Google Antigravity.
Agent platforms
Microsoft Copilot Studio plugs Postgate AI in as an MCP tool. Your Copilot agent then works with on-premises mailboxes. The same goes for n8n and for any other platform that speaks MCP with OAuth.
Your own agents
Any MCP-capable runtime can use the tools - from a Python script to a full agent platform.
Microsoft Exchange MCP servers compared
Other MCP servers
Most MCP servers for Exchange speak Microsoft Graph only, so they reach mailboxes in Exchange Online and nothing else. An Exchange Server in your own network stays out of reach.
Postgate AI
We connect Exchange on-premises via EWS, and Exchange Online via Microsoft Graph on top of that. Both run in the same multi-user server, either managed by us or self-hosted as a license. OAuth 2.0/PKCE, a per-user vault and central administration come with it, set up once for all employees.
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, Mistral Vibe 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. Either managed by us or self-hosted as a license - in both cases with no installation on clients.
Can I use the MCP server in Copilot Studio or n8n?
Yes, both work. In Microsoft Copilot Studio you add Postgate AI as an MCP tool (Streamable HTTP, OAuth 2.0 with dynamic discovery) and your Copilot agent then reaches on-premises mailboxes. n8n works the same way. In both cases every user works with their own Exchange permissions.
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 multi-user MCP server with OAuth 2.0/PKCE, an RSA-4096 vault per user, delegated permissions and central administration in the portal - either managed by us or as a self-hosted license.
Exchange as an MCP server - testable in minutes.
7 days free in the managed variant - connect your EWS URL, pair a client, use the tools. Self-hosted license on request.