Postfleet

What the Postfleet MCP server does

The Postfleet MCP server gives an AI agent access to email infrastructure managed by Postfleet. It can create and inspect mailboxes, manage domains, send messages, reply to existing messages, list inbox contents, read email, and wait for incoming mail. Postfleet processes inbound messages by parsing, classifying, extracting information to a schema, and screening for prompt injection before the agent reads the message.

The server also supports a draft-based approval workflow. An agent can create, list, retrieve, update, send, and delete drafts. When a message enters the approval gate, the send operation returns 202 pending_approval; that status means the message is awaiting approval rather than that delivery failed.

How it works

The Postfleet MCP server exposes the Postfleet API through MCP. Each tool is a thin wrapper around the corresponding /api/v1/ REST endpoint, so the API key controls authentication, resource scope, and quotas. A client can connect to the hosted endpoint at https://api.postfleet.ai/api/mcp using streamable HTTP and a Bearer token, or launch the npm package locally over stdio.

The hosted connection requires an Authorization header containing a pf_ API key. The local process reads the key from POSTFLEET_API_KEY. Separate keys can be used for separate workloads, which allows one key to be revoked without affecting other integrations. Postfleet documents different key scopes: bootstrap is limited to mailbox creation, api covers mail operations, and mcp is intended for MCP clients.

Setup and configuration

Create a pf_ API key through Postfleet, then choose a connection mode. For a hosted setup, configure the MCP client with the Postfleet MCP URL and a Bearer authorization header. A raw URL without the header will fail during initialization until authentication is supplied.

For local stdio, run:

npx -y @postfleet/mcp

Set POSTFLEET_API_KEY in the process environment. Claude Code can register the same command with its MCP configuration, and Cursor can use either the hosted endpoint or the local package. POSTFLEET_API_URL optionally changes the API origin from https://api.postfleet.ai, which supports staging or self-hosted deployments.

The repository is a mirror of source developed in the Postfleet application repository. The published local package is @postfleet/mcp; building from source uses npm install followed by npm run build.

Tools and capabilities

Available operations include:

• Create and list mailboxes.
• List, create, and verify domains.
• Send new email and reply to existing email.
• List inbox messages, read email, and wait for incoming mail.
• Create, inspect, update, send, and delete drafts.

The Postfleet MCP server is suited to agents that need asynchronous email interaction, structured inbound handling, or a human checkpoint before outbound messages are sent.

Limitations and notes

A valid API key is required, and keys are scoped to particular operations. Do not commit keys to source control or client configuration files that are shared insecurely. Hosted connections must send the Bearer header; configuring only the endpoint is insufficient. A send returning 202 pending_approval should be handled as an approval state rather than an error. The material does not specify delivery guarantees, mailbox limits, quota values, or supported email providers beyond Postfleet itself.