mailbox-mcp
Give your AI tools access to your email. Search, read, send, and manage messages across multiple accounts without leaving your terminal.
mailbox-mcp is an MCP server that connects your email to Claude Code, Cursor, Windsurf, or any AI tool that supports the Model Context Protocol. Instead of switching between your terminal and Gmail, you ask the AI to find that invoice, summarize a thread, or draft a reply — and it does.
What makes this different from the 60+ other email MCP servers:
- Multiple accounts, one server. Work email, personal email, client accounts — all accessible through a single server. No need to run separate instances.
- Not just Gmail. Supports Gmail (full API), any IMAP/SMTP provider (ProtonMail, corporate mail, self-hosted), and JMAP (Fastmail, Stalwart, Topicbox). Add providers without changing a line of tool code.
- Security-conscious. Encrypted credentials (AES-256-GCM), prompt injection fencing on email content, rate limiting, TLS enforcement, SSRF protection with IP encoding evasion detection, input validation.
- Tools for the workflows that matter. Search, read, send, reply, forward, drafts, labels, filters, templates, signatures, vacation replies, attachments, unsubscribe, and more.
- Zero native dependencies. Pure Node.js. Install and run anywhere.
Quick Start
Install
Add to your Claude Code MCP config (~/.claude.json). The package runs straight from npm via npx:
{
"mcpServers": {
"mailbox": {
"command": "npx",
"args": ["-y", "mailbox-mcp"],
"env": {
"MAILBOX_MCP_PASSPHRASE": "a-long-random-passphrase"
}
}
}
}
MAILBOX_MCP_PASSPHRASE is the passphrase used to encrypt IMAP/JMAP credentials at rest; it's required before adding an IMAP or JMAP account, and unused for Gmail-only setups.
From source instead
git clone https://github.com/jgalea/mailbox-mcp.git
cd mailbox-mcp
npm install && npm run build
Then point the config at the build with "command": "node", "args": ["/path/to/mailbox-mcp/dist/server.js"].
Add a Gmail Account
1. Create a Google Cloud project
- Go to Google Cloud Console and create a new project
- Enable the Gmail API: APIs & Services > Library > Gmail API > Enable
2. Set up OAuth consent screen
- Go to Google Auth Platform > Branding
- Set App name and User support email
- Go to Audience, select External
- Add the Google account you'll sign in with as a test user (this must be the exact
@gmail.com address you use to authenticate, not a workspace alias)
3. Create OAuth credentials
- Go to Google Auth Platform > Clients > Create Client
- Application type: Desktop app
- Click Create
- Go to APIs & Services > Credentials, find your client, and click the download icon to get the JSON
- Save the file as
~/.mailbox-mcp/oauth-keys.json
4. Authenticate
In Claude Code, run: authenticate alias="personal" provider="gmail" email="you@gmail.com"
This opens a browser window to complete the OAuth flow. Your tokens are stored locally in ~/.mailbox-mcp/accounts/.
Add an IMAP Account
In Claude Code, run:
authenticate alias="work" provider="imap" email="you@company.com" host="imap.company.com" smtpHost="smtp.company.com" username="you@company.com" password="<app-password>"
Credentials are encrypted at rest using AES-256-GCM.
Add a JMAP Account
In Claude Code, run:
authenticate alias="fastmail" provider="jmap" email="you@fastmail.com" host="fastmail.com" username="you@fastmail.com" password="<app-password>"
JMAP auto-discovers the API endpoint via .well-known/jmap. Credentials are encrypted at rest using AES-256-GCM.
Supported JMAP servers: Fastmail, Stalwart, Topicbox, Cyrus IMAP, and any RFC 8620-compliant server.
JMAP advantages over IMAP:
- Native thread support (real conversations, not synthetic)
- Server-side search (faster, more accurate)
- Batch operations in a single HTTP request
- No persistent connection required
Universal (Gmail + IMAP + JMAP)
| Tool | Description |
|---|
list_accounts | List configured accounts |
authenticate | Add a new account |
reauth | Re-run OAuth for an existing Gmail account (use when refresh token expires with invalid_grant) |
remove_account | Remove an account |
search_emails | Search messages (optional folder to scope the search) |
multi_account_search | Run the same query across every configured account in parallel |
read_email | Read a message |
read_thread | Read a conversation thread (Gmail + JMAP) |
send_email | Send a new email (supports from, attachments) |
reply_email | Reply to a message (supports from, attachments) |
forward_email | Forward a message (supports from, attachments) |
create_draft | Create a draft (supports reply drafts via in_reply_to, plus from, attachments) |
list_drafts | List drafts for an account |
send_draft | Send an existing draft |
trash_emails | Trash messages |
mark_read | Mark a message as read or unread |
star_email | Star or unstar a message |
archive_email | Archive a message (remove from inbox) |
list_labels | List labels/folders |
create_label | Create a label/folder |
delete_label | Delete a label/folder |
modify_email | Modify message labels |
batch_modify_emails | Bulk modify labels |
bulk_modify | Add/remove labels on every message matching a query (search-then-batch; dry_run supported) |
bulk_trash | Trash every message matching a query (dry_run supported) |
list_recent_bulk_ops | List recorded bulk operations from the transaction log |
undo_bulk_op | Reverse a recorded bulk operation against the exact ids it touched |
count_unread_by_label | Show unread message counts per label/folder |
download_attachment | Download an attachment |
export_email | Save a message as a .eml file |
export_thread | Save every message in a thread as .eml files (Gmail + JMAP) |
emails_since | List messages received after a given timestamp |
inbox_summary | Inbox overview |
Gmail-Only
| Tool | Description |
|---|
update_draft | Replace the contents of an existing draft (thread association preserved) |
delete_draft | Permanently delete a draft |
create_filter | Create a filter |
list_filters | List filters |
delete_filter | Delete a filter |
save_template | Save a template |
list_templates | List templates |
delete_template | Delete a template |
send_template | Send from template |
get_signature | Get signature |
set_signature | Update signature |
get_vacation | Get vacation settings |
set_vacation | Configure vacation reply (supports date ranges, domain-only) |
unsubscribe | Find unsubscribe link |
bulk_unsubscribe | Bulk unsubscribe |
list_send_as | List send-as aliases |
49 tool schemas cost roughly 6,000 tokens in clients that load every definition into context. In everyday use a handful of tools do most of the work, so you can expose only the groups you need with MAILBOX_MCP_TOOLS (comma-separated). Unset means everything loads.
"env": {
"MAILBOX_MCP_TOOLS": "core,attachments"
}
| Group | Tools | What it covers |
|---|
core | 19 | accounts, search, read, send, reply, forward, drafts, inbox summary (~2,900 tokens) |
organize | 9 | labels, star, archive, trash, modify |
bulk | 4 | query-wide modify/trash with dry-run and undo |
attachments | 3 | download attachments, export .eml |
gmail-extras | 14 | filters, templates, signatures, vacation, unsubscribe, send-as |
Calls to tools in disabled groups fail with an error naming the group to enable.
Sending attachments
send_email, reply_email, forward_email, and create_draft accept an optional attachments parameter — an array of local file paths. The server reads each file, detects its MIME type from the extension, and embeds it in the outgoing message (or draft).
send_email account="personal" to=["friend@example.com"] subject="The report" body="See attached." attachments=["/path/to/report.pdf", "/path/to/chart.png"]
- Each file must be a regular file ≤ 25 MB; total per message is capped at 25 MB (Gmail's hard limit).
- Paths are resolved through any symlinks, and filenames are stripped of CRLF before going into headers.
- Gmail routes messages with attachments through the multipart upload endpoint (35 MB API limit) instead of the JSON endpoint, so the 25 MB message cap is the real ceiling.
- JMAP uploads each file to the server's upload URL first, then references the resulting blobIds in the Email/set call.
Choosing the sender address
One account often speaks for several addresses. send_email, reply_email, forward_email, create_draft, and update_draft accept an optional from parameter; without it, the account's primary address is used.
reply_email account="personal" message_id="18f..." from="jean@example.com" body="Thanks, sorted."
Accepted forms are alias@example.com and Name <alias@example.com>; matching is case-insensitive.
The address is checked against the account before anything is sent, and the call fails with the list of usable addresses if it doesn't match. This matters because Gmail silently falls back to the primary address when the From header names an address you haven't verified, so a message can be sent from the wrong identity and still look like it succeeded. Some recipients (Amazon's customer service, for one) reject mail that doesn't come from the address on file.
- Gmail: the address must be a send-as alias with verification completed. Run
list_send_as to see them. Pending aliases are refused.
- JMAP: the address must match one of the account's identities; its
identityId is attached to the submission.
- IMAP: no alias list exists to check against, so any
from is passed to the SMTP relay, which accepts or rejects it at send time.
License
MIT
Built at AgentVania.