Email Client MCP

Multi-account email MCP server with reliable IMAP-to-mailboxes sync into a Drive-backed messagesStore (@diskd-ai/sdk). Read tools hit IMAP live; the watcher mirrors every configured account into the workspace store on an interval (>= 60s).

Address: end:comm/email-client-mcp.

Install

npx -y @diskd-ai/email-client-mcp stdio

The server speaks Model Context Protocol over stdio. JSON-RPC on stdout; logs to stderr.

Tools

All read tools fetch from IMAP live (BODY.PEEK, never silently flips \Seen):

• list_accounts -- enumerate configured accounts (config-only; no IMAP).
• list_mailbox_folder -- folders for an account, with optional unread counts and special-use flags.
• find_mailbox_folder -- resolve real folders containing a given Message-Id (use before move_email for Gmail virtuals).
• list_emails -- paginated metadata listing with filters (unread, flagged, from/to/subject, since).
• get_email -- single message by UID. Formats: raw, text (HTML stripped), stripped (also drops quoted replies + signatures). markRead=true opt-in.
• get_emails -- bulk variant of get_email (max 20).
• move_email -- IMAP MOVE between folders. Refuses virtual mailboxes (e.g. [Gmail]/All Mail).
• set_email_attributes -- set read/unread and flagged/unflagged state for IMAP messages, then patch the Drive mirror.
• bulk_action -- mark_read | mark_unread | flag | unflag | move | delete over up to 100 UIDs.
• get_watcher_status -- in-memory snapshot of the sync watcher.

Watcher reliability

The watcher synchronizes IMAP into the workspace messagesStore on every tick. Invariants:

1. lastSyncedUid advances only after a successful idempotent upsertBatch.
2. externalId = "${UIDVALIDITY}:${UID}" so a UIDVALIDITY rollover never collides with the previous generation.
3. UIDVALIDITY mismatch on a folder triggers a clean drop + resync.
4. Per-account in-flight lock: an overlapping tick is skipped, never queued.
5. Folder metadata is the durable checkpoint -- restart resumes from there, never from in-memory state.
6. Folders deleted in IMAP are pruned from Drive at the end of a tick.
7. Sliding-window flag reconciliation bounds drift to flag_reconcile_window UIDs per tick.
8. One rotating maintenance folder per tick prunes Drive messages that moved or disappeared in IMAP.

Tick interval is clamped to >= 60s.

Configuration

Default path: ~/.config/email-client-mcp/config.toml (override via EMAIL_CLIENT_MCP_CONFIG). When deployed by mcp-hub the file is mounted by the diskd-ai/email-client-mcp vault assembler.

[sdk]
api_key = "..."
base_url = "https://apis.example/"
# workspace_id falls back to MCP_HUB_WORKSPACE_ID env when omitted.

[watcher]
enabled = true
interval_ms = 60000
flag_reconcile_window = 500
# folders = ["INBOX", "Sent"]   # optional allowlist; empty = all

[[accounts]]
name = "work"
email = "[email protected]"
full_name = "You"
password = "..."

[accounts.imap]
host = "imap.example.com"
port = 993
tls = true
verify_ssl = false

For Gmail OAuth accounts, replace the password field with an [accounts.oauth2] block:

[[accounts]]
name = "gmail-work"
email = "[email protected]"
full_name = "You"

[accounts.oauth2]
provider = "google"
client_id = "..."
client_secret = "..."
refresh_token = "..."

[accounts.imap]
host = "imap.gmail.com"
port = 993
tls = true
verify_ssl = false

Development

bun install
bun run typecheck
bun run lint
bun run test          # vitest unit tests
bun run build         # tsc -> dist/
bun run start         # node dist/server.js stdio (needs config TOML)
bun run dev           # tsx src/server.ts stdio (live reload)

# stdio smoke test (initialize + tools/list + tool calls):
node scripts/smoke.mjs

Releasing

Auto-publish via .github/workflows/release.yml:

• Tag-driven (preferred): npm version patch && git push --follow-tags from main; the v*.*.* tag triggers the workflow which typechecks, lints, tests, builds, and npm publishes.
• One-click: in the GitHub Actions UI run the Release workflow with bump = patch | minor | major. The job bumps package.json, commits, tags, pushes, and publishes -- all in one job.

Both paths run bun install --frozen-lockfile, bun run typecheck, bun run lint, bun run test, and bun run build before publishing, with provenance attestation enabled.

Required repo secret:

License

LGPL-3.0-or-later. See LICENSE.