____  ____   ___ _____ ___  _   _   __  __    _    ___ _
 |  _ \|  _ \ / _ \_   _/ _ \| \ | | |  \/  |  / \  |_ _| |
 | |_) | |_) | | | || || | | |  \| | | |\/| | / _ \  | || |
 |  __/|  _ <| |_| || || |_| | |\  | | |  | |/ ___ \ | || |___
 |_|   |_| \_\\___/ |_| \___/|_| \_| |_|  |_/_/   \_\___|_____|
  Bridge Client  ·  CLI + Claude Desktop MCP for Proton Mail

Proton Mail Bridge Client

A full-featured CLI and Claude Desktop MCP for Proton Mail, built on top of Proton Bridge.

About

Proton Mail Bridge Client gives you two ways to use Proton Mail programmatically:

CLI — a terminal client with complete parity to the MCP surface. Read, search, send, draft, archive, manage folders, triage threads, and run diagnostics — all from the command line. Body can be piped via stdin. Output is either human-readable or --json.

MCP server — the same capabilities exposed as a Model Context Protocol server so Claude Desktop can read and manage your Proton Mail in any chat, on the same machine where Proton Bridge is running.

Both surfaces share the same backend: Proton Bridge IMAP and SMTP, a local SQLite index, and an audit log. No hosted relay, no remote URL, no cloud dependency beyond your own Proton account.

Prerequisites

• Node.js 18+
• Proton Bridge installed and signed in
• From Bridge: IMAP host/port, SMTP host/port, username, Bridge password

Default local Bridge addresses: IMAP 127.0.0.1:1143, SMTP 127.0.0.1:1025

Install

Before running npm run build: configure your credentials first — see Environment below. The build step connects to Proton Bridge to verify connectivity and will fail without credentials set.

git clone https://github.com/googlarz/proton-mail-bridge-client.git
cd proton-mail-bridge-client
npm install
npm run build

After install, the proton-mail-bridge-client (and proton-mail-bridge) binary is available from the repo.

For a system-wide install: npm install -g .

CLI

proton-mail-bridge-client <command> [options]

All commands support --json for machine-readable output.

Read

proton-mail-bridge-client emails --folder INBOX --limit 25
proton-mail-bridge-client read INBOX::25642
proton-mail-bridge-client search "invoice" --limit 10
proton-mail-bridge-client search --live --from openai.com
proton-mail-bridge-client attachments INBOX::25642

Triage

proton-mail-bridge-client digest
proton-mail-bridge-client threads "quarterly review"
proton-mail-bridge-client actionable
proton-mail-bridge-client followups
proton-mail-bridge-client thread-brief <threadId>
proton-mail-bridge-client document-threads --category invoice
proton-mail-bridge-client meeting-context [email protected]

Compose & send

proton-mail-bridge-client send --to [email protected] --subject "Hey" --body "Hello"
echo "Hello" | proton-mail-bridge-client send --to [email protected] --subject "Hey"
proton-mail-bridge-client reply INBOX::25642 --body "On it."
proton-mail-bridge-client reply INBOX::25642 --reply-all --body "On it."
proton-mail-bridge-client forward INBOX::25642 --to [email protected]

Mailbox actions

proton-mail-bridge-client move INBOX::25642 Folders/Archive
proton-mail-bridge-client archive INBOX::25642
proton-mail-bridge-client trash INBOX::25642
proton-mail-bridge-client restore Trash::25642
proton-mail-bridge-client mark-read INBOX::25642
proton-mail-bridge-client mark-read INBOX::25642 --unread
proton-mail-bridge-client star INBOX::25642
proton-mail-bridge-client delete INBOX::25642
proton-mail-bridge-client batch archive INBOX::100,INBOX::101,INBOX::102
proton-mail-bridge-client thread-action <threadId> archive

Folders

proton-mail-bridge-client folders
proton-mail-bridge-client create-folder Folders/Receipts
proton-mail-bridge-client rename-folder Folders/Receipts Folders/Bills
proton-mail-bridge-client delete-folder Folders/Bills

Drafts

proton-mail-bridge-client drafts
proton-mail-bridge-client draft-create --to [email protected] --subject "Draft" --body "..."
proton-mail-bridge-client draft-read <id>
proton-mail-bridge-client draft-update <id> --subject "Updated subject"
proton-mail-bridge-client draft-reply INBOX::25642 --body "Will do."
proton-mail-bridge-client draft-forward INBOX::25642 --to [email protected]
proton-mail-bridge-client draft-sync <id>
proton-mail-bridge-client draft-send <id>
proton-mail-bridge-client draft-delete <id>
proton-mail-bridge-client remote-drafts

Analytics & diagnostics

proton-mail-bridge-client stats
proton-mail-bridge-client analytics
proton-mail-bridge-client contacts
proton-mail-bridge-client volume-trends --days 14
proton-mail-bridge-client watch --timeout 30
proton-mail-bridge-client test-email [email protected]
proton-mail-bridge-client doctor
proton-mail-bridge-client status
proton-mail-bridge-client sync --folder INBOX --limit 150

MCP tool passthrough

Any MCP tool is also callable directly from the CLI:

proton-mail-bridge-client tools
proton-mail-bridge-client tool get_connection_status --json
proton-mail-bridge-client tool search_indexed_emails --args '{"query":"invoice","limit":3}'

Environment

The CLI and MCP server both read the same environment variables:

export PROTONMAIL_USERNAME='[email protected]'
export PROTONMAIL_PASSWORD='your-bridge-password'
export PROTONMAIL_IMAP_HOST='127.0.0.1'
export PROTONMAIL_IMAP_PORT='1143'
export PROTONMAIL_IMAP_SECURE='false'
export PROTONMAIL_SMTP_HOST='127.0.0.1'
export PROTONMAIL_SMTP_PORT='1025'
export PROTONMAIL_DATA_DIR="$HOME/.proton-mail-bridge-client"

Optional secrets via file or command (avoids raw credentials in shell):

export PROTONMAIL_USERNAME_FILE='/path/to/user.txt'
export PROTONMAIL_PASSWORD_FILE='/path/to/pass.txt'
# or
export PROTONMAIL_USERNAME_COMMAND='pass proton/username'
export PROTONMAIL_PASSWORD_COMMAND='pass proton/password'

Full runtime flags:

export PROTONMAIL_READ_ONLY='false'
export PROTONMAIL_ALLOW_SEND='true'
export PROTONMAIL_ALLOW_REMOTE_DRAFT_SYNC='true'
export PROTONMAIL_ALLOWED_ACTIONS='mark_read,mark_unread,star,unstar,archive,trash,restore'
export PROTONMAIL_AUTO_SYNC='true'
export PROTONMAIL_STARTUP_SYNC='true'
export PROTONMAIL_SYNC_INTERVAL_MINUTES='5'
export PROTONMAIL_IDLE_WATCH='true'
export PROTONMAIL_IDLE_MAX_SECONDS='30'

Claude Desktop Setup

To use Proton Mail Bridge Client with Claude Desktop, run the guided wizard:

npm run setup:claude-desktop

This will:

• check your local Bridge ports
• ask for your Bridge username and password
• build the project
• install a stable machine-wide runtime
• write the Claude Desktop MCP config entry

After setup: restart Claude Desktop, keep Proton Bridge open, then check + → Connectors → proton-mail-bridge.

The runtime is installed at:

• macOS: ~/Library/Application Support/Proton Mail Bridge Client
• Linux: ~/.local/share/proton-mail-bridge-client
• Windows: %APPDATA%\Proton Mail Bridge Client

Updating

git pull
npm run update:claude-desktop

Manual Claude Desktop config

Three credential methods are supported. Use whichever fits your setup:

Option 1 — Environment variables (simplest):

{
  "mcpServers": {
    "proton-mail-bridge": {
      "command": "node",
      "args": ["/path/to/runtime/dist/index.js"],
      "cwd": "/path/to/runtime",
      "env": {
        "PROTONMAIL_USERNAME": "[email protected]",
        "PROTONMAIL_PASSWORD": "your-bridge-password",
        "PROTONMAIL_IMAP_HOST": "127.0.0.1",
        "PROTONMAIL_IMAP_PORT": "1143",
        "PROTONMAIL_IMAP_SECURE": "false",
        "PROTONMAIL_SMTP_HOST": "127.0.0.1",
        "PROTONMAIL_SMTP_PORT": "1025"
      }
    }
  }
}

Option 2 — File-based secrets (credentials in files, not config):

{
  "mcpServers": {
    "proton-mail-bridge": {
      "command": "node",
      "args": ["/path/to/runtime/dist/index.js"],
      "cwd": "/path/to/runtime",
      "env": {
        "PROTONMAIL_USERNAME_FILE": "/path/to/username.txt",
        "PROTONMAIL_PASSWORD_FILE": "/path/to/password.txt",
        "PROTONMAIL_IMAP_HOST": "127.0.0.1",
        "PROTONMAIL_IMAP_PORT": "1143",
        "PROTONMAIL_IMAP_SECURE": "false",
        "PROTONMAIL_SMTP_HOST": "127.0.0.1",
        "PROTONMAIL_SMTP_PORT": "1025"
      }
    }
  }
}

Option 3 — Command-based secrets (recommended for pass, gopass, or any secret manager):

{
  "mcpServers": {
    "proton-mail-bridge": {
      "command": "node",
      "args": ["/path/to/runtime/dist/index.js"],
      "cwd": "/path/to/runtime",
      "env": {
        "PROTONMAIL_USERNAME_COMMAND": "pass proton/username",
        "PROTONMAIL_PASSWORD_COMMAND": "pass proton/password",
        "PROTONMAIL_IMAP_HOST": "127.0.0.1",
        "PROTONMAIL_IMAP_PORT": "1143",
        "PROTONMAIL_IMAP_SECURE": "false",
        "PROTONMAIL_SMTP_HOST": "127.0.0.1",
        "PROTONMAIL_SMTP_PORT": "1025"
      }
    }
  }
}

macOS note

On macOS, better-sqlite3 must be a native binary built for the current machine. The installer handles this automatically. If you restore from another environment or see a native-module crash, run npm run update:claude-desktop.

Trust & Safety

• Runs entirely locally — no hosted relay, no remote URL.
• Talks to Proton Mail only through Proton Bridge on your own machine.
• PROTONMAIL_READ_ONLY=true disables all write operations.
• PROTONMAIL_ALLOW_SEND=false disables SMTP sends without affecting other writes.
• PROTONMAIL_ALLOWED_ACTIONS controls which mailbox mutations are permitted.
• batch_email_action and apply_thread_action both support dryRun: true.
• Supports *_FILE and *_COMMAND secrets so raw credentials never appear in config or shell history.
• System folders (INBOX, Sent, Trash, Spam, Archive, All Mail) are guarded against accidental deletion.

Compared With Claude's Native Gmail Connector

Example Claude Workflows

Once connected, ask Claude anything. Some prompts that work well:

Morning triage

"Give me a digest of my inbox. Flag anything that needs a reply today and anything that looks like a bill or invoice."

Inbox zero session

"Go through my unread emails from the past 3 days. Archive newsletters, trash anything promotional, and tell me what's left that needs action."

Folder filing

"Find all emails from stripe.com and move them to Folders/Receipts. Create the folder if it doesn't exist."

Meeting prep

"I have a call with [email protected] in an hour. Pull up our last 5 email threads and summarise the open items."

Draft review

"Show me my drafts, pick the oldest one, and suggest a better subject line and closing paragraph."

Tip: If Claude needs to create a folder before moving emails, remind it to use Folders/Name (not just Name) — that's the Proton Bridge namespace for real folders vs. labels.

Tool Surface

Send

send_email · send_test_email · reply_to_email · forward_email

Drafts

create_draft · create_reply_draft · create_forward_draft · create_thread_reply_draft · list_drafts · list_remote_drafts · get_draft · update_draft · sync_draft_to_remote · send_draft · delete_draft

Read

get_emails · get_email_by_id · search_emails · list_attachments · get_attachment_content · save_attachments · save_attachment

Triage

get_folders · sync_folders · get_labels · get_threads · get_thread_by_id · get_thread_brief · get_actionable_threads · get_inbox_digest · get_follow_up_candidates · find_document_threads · prepare_meeting_context

Actions

mark_email_read · star_email · move_email · archive_email · trash_email · restore_email · delete_email · batch_email_action · apply_thread_action

Folder management

create_folder · rename_folder · delete_folder

Analytics

get_email_stats · get_email_analytics · get_contacts · get_volume_trends

Diagnostics

get_connection_status · get_runtime_status · run_doctor · get_audit_logs · run_background_sync · wait_for_mailbox_changes · sync_emails · get_index_status · search_indexed_emails · clear_cache · clear_index · get_logs

Operational Notes

• get_emails and search_emails return a composite emailId — use it for reads and actions.
• The local index lives at PROTONMAIL_DATA_DIR/mail-index.sqlite.
• Audit logs live at PROTONMAIL_DATA_DIR/audit.log.
• Background sync and IMAP IDLE keep the index warm but depend on Bridge staying up.
• search_indexed_emails supports from:, to:, subject:, label:, domain: shortcuts.
• Draft sync is best-effort — local draft is always preserved even if remote sync fails.

License

MIT