ox-mcp

An MCP server for Open-Xchange and standards-based mail platforms — read & search email, send & reply, manage server-side filters, calendar events and invitations, contacts, and other people's availability (free/busy), across one or many accounts.

It speaks standard IMAP + SMTP + ManageSieve + CalDAV + CardDAV with RFC 6638 free/busy, so it works with any Open-Xchange deployment or standards-compliant host. Authenticate with your email + app password (the same credential DAVx5 uses) or OAuth2/OIDC.

No affiliation with Open-Xchange.

Install / run

npx -y @rheopyrin/ox-mcp
# or with a custom config location:
npx -y @rheopyrin/ox-mcp --config /path/to/config.json

MCP client config (Claude Desktop / Claude Code):

{
  "mcpServers": {
    "ox": {
      "command": "npx",
      "args": ["-y", "@rheopyrin/ox-mcp"],
      "env": {
        "OX_MCP_MAIL_SERVER": "mail.example.com",
        "OX_MCP_MAIL_USER": "you@yourdomain.com",
        "OX_MCP_MAIL_APP_PASSWORD": "xxxx-xxxx-xxxx-xxxx",
        "OX_MCP_CALDAV_SERVER": "dav.example.com",
        "OX_MCP_CALDAV_USER": "you@yourdomain.com",
        "OX_MCP_CALDAV_APP_PASSWORD": "yyyy-yyyy-yyyy-yyyy"
      }
    }
  }
}

On first run (without --config) it creates ~/.ox-mcp/config.json (permissions 0600) with every feature flag listed — reads enabled, writes disabled — and empty hosts for you to fill in.

--config

--config <file> (or env OX_MCP_CONFIG; the flag wins) loads an explicit config file instead of ~/.ox-mcp/config.json. The file must exist — nothing is auto-created when the override is used.

Related MCP server: outlook-mcp

Tools

Tools are grouped by protocol domain. A group's tools appear only when enabled, and the group's server host must be configured (see Validation).

• Every tool (except list_servers) accepts an optional server argument to target a specific account. A tool is hidden from the tool list unless its flag is enabled for at least one account.

• email_search searches all folders by default; pass folder to narrow it. On the ox-api transport, body/text match only the subject and addresses of recent messages — use transport: "imap" for true full-text search.

• email_mark_spam / email_archive find the Junk/Archive folder via IMAP special-use attributes, with name-based fallbacks.

• email_reply / email_reply_all preserve threading (In-Reply-To/References) and exclude your own address from reply-all recipients.

• The three RSVP tools (calendar_accept_event / calendar_decline_event / calendar_tentative_event) share one feature flag: respondEvent (calDav section). They rewrite your PARTSTAT on the invitation; the server notifies the organizer.

• contact_find searches contacts server-side (CardDAV addressbook-query, RFC 6352) with automatic fallback to client-side filtering; fields narrows the match to name/email/phone/org (default name + email). Handy for resolving a name to an email before calendar_free_busy. contact_list is plain enumeration.

Mail filters

email_filter_create / email_filter_update manage server-side sieve filters over ManageSieve (port 4190, STARTTLS; requires basic/app-password auth). Rules support conditions on from/to/subject/any header (AND or OR) and actions fileinto (move to folder), discard, markRead, redirect.

Backend depends on mail.transport: with ox-api (default), filters go through the OX mailfilter/v2 module and operate on the account's real webmail rules (rules with tests/actions beyond this model are listed read-only as other). With imap, ox-mcp manages its own sieve script over ManageSieve (port 4190) and activates it — filters from other scripts become inactive while it is active.

Configuration: per-protocol sections

Each account is made of up to three self-contained sections — mail, calDav, cardDav — each with its own server, auth (incl. its own login user), and features. This matches servers (like Open-Xchange) that scope app passwords per protocol: your Mail password, CalDAV password, and CardDAV password can all differ.

{
  "defaultServer": "default",
  "timeoutSeconds": 300,                                     // optional; request timeout, default 300
  "servers": {
    "default": {
      "mail": {
        "server": "webmail.example.com",                    // OX HTTP API host (default transport)
        "transport": "ox-api",                              // optional; "imap" for direct IMAP/SMTP
        "imap": { "host": "imap.example.com", "port": 993 }, // optional overrides
        "smtp": { "host": "smtp.example.com", "port": 587, "secure": false }, // secure optional; 993/465 = TLS, else STARTTLS
        "auth": { "type": "basic", "user": "me@example.com", "appPassword": "mail-scoped-pw" },
        "features": { "search": true, "send": false /* per-tool flags */ }
      },
      "calDav": {
        "server": "dav.example.com",
        "auth": { "type": "basic", "user": "me@example.com", "appPassword": "caldav-scoped-pw" },
        "features": { "respondEvent": false /* … */ }
      },
      "cardDav": {
        "server": "dav.example.com",
        "auth": { "type": "basic", "user": "me@example.com", "appPassword": "carddav-scoped-pw" }
      }
    }
  }
}

• A section you don't configure = its tools are disabled. A calDav-only config is perfectly valid.

• mail.transport is optional and defaults to "ox-api" — the Open-Xchange HTTP API (the webmail backend, https://<server>/appsuite/api). OX deployments validate app passwords at this middleware, so it works even where raw IMAP rejects them; server is the webmail host. Filter tools use the OX mailfilter/v2 module — they list and edit the account's actual webmail rules. Caveat: search matches subject/addresses (not full bodies).

• Set transport: "imap" for direct IMAP/SMTP against generic (non-OX) mail hosts — then server is the mail host, with optional split imap/smtp endpoints.

• enabled: false on a section is a config master switch for all its tools.

• There is no global features block — flags live only inside sections (env vars remain global).

Feature flags

Resolution precedence — env always beats config, first defined wins:

1. per-account env, tool — OX_MCP_<ID>_ENABLE_EMAIL_SEND

2. per-account env, group — OX_MCP_<ID>_ENABLE_MAIL

3. global env, tool — OX_MCP_ENABLE_EMAIL_SEND

4. global env, group — OX_MCP_ENABLE_MAIL / _CALDAV / _CARDDAV

5. section config, tool — servers.<id>.mail.features.send

6. section config, master — servers.<id>.mail.enabled

7. default — true for reads, false for writes

# enable sending on all accounts
OX_MCP_ENABLE_EMAIL_SEND=true
# turn off the whole calendar section
OX_MCP_ENABLE_CALDAV=false
# enable event creation only on the "work" account
OX_MCP_WORK_ENABLE_CALENDAR_CREATE_EVENT=true
# enable all three RSVP tools at once
OX_MCP_ENABLE_CALENDAR_RESPOND_EVENT=true

Booleans accept true/1/yes/on and false/0/no/off.

Connection & credentials (env)

Every section field is settable via env: OX_MCP_[ID_]<SECTION>_<FIELD> with SECTION ∈ MAIL | CALDAV | CARDDAV. The default account uses the non-indexed form.

Default ports: IMAP 993, SMTP 465, DAV 443, ManageSieve 4190. TLS mode derives from the port (993/465 implicit TLS; 143/587 STARTTLS) unless secure is set explicitly.

Validation

Configuration is validated strictly at startup: every present section with enabled tools must have a server (or split imap/smtp hosts for mail) and a login user, or the server exits with an error naming the exact field. Accounts with zero sections error too. Absent sections are simply disabled — no error.

Authentication types

basic (app password) is the default. Other Open-Xchange-aligned mechanisms are supported per section via auth.type / OX_MCP_[ID_]<SECTION>_AUTH_TYPE:

Tokens are cached and refreshed automatically. Note: mail filters (ManageSieve) require basic auth.

Multiple accounts

OX_MCP_ACCOUNTS=work,personal
OX_MCP_WORK_MAIL_SERVER=mail.work.com
OX_MCP_WORK_MAIL_USER=me@work.com
OX_MCP_WORK_MAIL_APP_PASSWORD=...
OX_MCP_PERSONAL_CALDAV_SERVER=dav.personal.com
OX_MCP_PERSONAL_CALDAV_USER=me@personal.com
OX_MCP_PERSONAL_CALDAV_APP_PASSWORD=...
OX_MCP_DEFAULT_SERVER=work

Or define them in ~/.ox-mcp/config.json under servers (keyed by id). list_servers shows what's configured (never secrets); env values override config field-by-field. Feature flags can differ per account (e.g. sending enabled only on work).

Free/busy caveat

calendar_free_busy returns availability windows only (busy/free), via the CalDAV scheduling outbox — no calendar sharing needed. It does not reveal event details, and requires the server to advertise a schedule-outbox-URL. To read a colleague's full calendar, they must share it with your account; shared calendars then appear in calendar_list / calendar_list_events.

Docker

docker build -t ox-mcp .
docker run -i --rm \
  -e OX_MCP_MAIL_SERVER=mail.example.com \
  -e OX_MCP_MAIL_USER=you@yourdomain.com \
  -e OX_MCP_MAIL_APP_PASSWORD=xxxx \
  ox-mcp

Development

npm install
npm run dev          # run from source
npm test             # vitest
npm run test:coverage
npm run build        # bundle to dist/ (tsup)

License

MIT