jmap-mcp

MCP server exposing JMAP email and Sieve script operations as tools.

Built with the Go MCP SDK (go-sdk) and go-jmap library.

Tools

Tools map closely to JMAP methods. Email mutation tools provide structured convenience wrappers over Email/set patches.

Mailbox (RFC 8621)

Tool	JMAP Method	Description
mailbox_get	Mailbox/get	Get mailboxes by ID, or list all
mailbox_set	Mailbox/set	Create, update, or destroy mailboxes

Email (RFC 8621)

Tool	JMAP Method	Description
email_query	Email/query	Search emails with filters, returns IDs and total count
email_get	Email/get	Get full content of emails by ID
email_create	Email/set	Create a new email draft in the Drafts mailbox
email_move	Email/set	Move emails to a different mailbox
email_flag	Email/set	Set or remove flags (seen, flagged, answered, draft)
email_delete	Email/set	Delete emails (move to Trash or permanently destroy)

Identity

Tool	JMAP Method	Description
identity_get	Identity/get	List sender identities (email addresses)

Submission (feature-gated)

Tool	JMAP Method	Description
email_submission_set	EmailSubmission/set	Submit a draft for delivery (requires -enable-send)

Sieve Scripts (RFC 9661, feature-gated)

Tool	JMAP Method	Description
sieve_get	SieveScript/get	List all scripts, or get one with full content (requires -enable-sieve)
sieve_set	SieveScript/set	Create, update, or destroy Sieve scripts (requires -enable-sieve)
sieve_validate	SieveScript/validate	Validate a Sieve script without saving (requires -enable-sieve)

Configuration

Env var	Required	Description
JMAP_SESSION_URL	always	JMAP session endpoint (e.g. https://api.fastmail.com/jmap/session)
JMAP_AUTH_TOKEN	stdio mode	Bearer token for JMAP authentication

Flag	Default	Description
-mode	stdio	Server mode: stdio or http
-listen	:8080	HTTP listen address (http mode only)
-enable-send	false	Enable the email_submission_set tool (off by default)
-enable-sieve	false	Enable Sieve script tools (off by default, requires JMAP server support)

In HTTP mode, the token can be passed per-request via Authorization: Bearer <token> header or jmap_token query parameter (query parameter takes precedence).

Installation

Kubernetes (Helm)

helm install jmap-mcp oci://ghcr.io/mikluko/helm-charts/jmap-mcp \
  --version 0.1.0 \
  --set jmap.sessionURL="https://api.fastmail.com/jmap/session"

In HTTP mode, JMAP auth tokens are passed per-request via Authorization: Bearer header or ?jmap_token= query parameter — no static tokens are stored in the cluster.

Binary

go install github.com/mikluko/jmap-mcp@latest

From source

git clone https://github.com/mikluko/jmap-mcp.git
cd jmap-mcp
make install

Usage

# stdio mode (default)
export JMAP_SESSION_URL=https://api.fastmail.com/jmap/session
export JMAP_AUTH_TOKEN=your-token
./jmap-mcp

# HTTP mode
./jmap-mcp -mode http -listen :8080

Build

make build # Build and push container image + Helm chart
make image # Build and push container image with ko
make package # Package and push Helm chart to OCI registry
make test # Run tests
make install # Install binary locally

References

• RFC 8620 — JMAP Core
• RFC 8621 — JMAP Mail
• RFC 9425 — JMAP Sieve Scripts
• MCP Specification