MCP Email Server

mcp-email-server

IMAP and SMTP via MCP Server

• Github repository: https://github.com/ai-zerolab/mcp-email-server/

• Documentation https://ai-zerolab.github.io/mcp-email-server/

Development

This project is managed using uv.

Try make install to install the virtual environment and install the pre-commit hooks.

Use uv run mcp-email-server for local development.

Releasing a new version

• Create an API Token on PyPI.

• Add the API Token to your projects secrets with the name PYPI_TOKEN by visiting this page.

• Create a new release on Github.

• Create a new tag in the form *.*.*.

For more details, see here.

Installation

Manual Installation

We recommend using uv to manage your environment.

Try uvx mcp-email-server@latest ui to config, and use following configuration for mcp client:

{
 "mcpServers": {
 "zerolib-email": {
 "command": "uvx",
 "args": ["mcp-email-server@latest", "stdio"]
 }
 }
}

This package is available on PyPI, so you can install it using pip install mcp-email-server

After that, configure your email server using the ui: mcp-email-server ui

Environment Variable Configuration

You can also configure the email server using environment variables, which is particularly useful for CI/CD environments like Jenkins. zerolib-email supports both UI configuration (via TOML file) and environment variables, with environment variables taking precedence.

{
 "mcpServers": {
 "zerolib-email": {
 "command": "uvx",
 "args": ["mcp-email-server@latest", "stdio"],
 "env": {
 "MCP_EMAIL_SERVER_ACCOUNT_NAME": "work",
 "MCP_EMAIL_SERVER_FULL_NAME": "John Doe",
 "MCP_EMAIL_SERVER_EMAIL_ADDRESS": "[email protected]",
 "MCP_EMAIL_SERVER_USER_NAME": "[email protected]",
 "MCP_EMAIL_SERVER_PASSWORD": "your_password",
 "MCP_EMAIL_SERVER_IMAP_HOST": "imap.gmail.com",
 "MCP_EMAIL_SERVER_IMAP_PORT": "993",
 "MCP_EMAIL_SERVER_SMTP_HOST": "smtp.gmail.com",
 "MCP_EMAIL_SERVER_SMTP_PORT": "465"
 }
 }
 }
}

Available Environment Variables

Variable Description Default Required MCP_EMAIL_SERVER_ACCOUNT_NAME Account identifier "default" No MCP_EMAIL_SERVER_FULL_NAME Display name Email prefix No MCP_EMAIL_SERVER_EMAIL_ADDRESS Email address - Yes MCP_EMAIL_SERVER_USER_NAME Login username Same as email No MCP_EMAIL_SERVER_PASSWORD Email password - Yes MCP_EMAIL_SERVER_IMAP_HOST IMAP server host - Yes MCP_EMAIL_SERVER_IMAP_PORT IMAP server port 993 No MCP_EMAIL_SERVER_IMAP_SSL Enable IMAP SSL true No MCP_EMAIL_SERVER_IMAP_START_SSL Enable IMAP STARTTLS false No MCP_EMAIL_SERVER_IMAP_VERIFY_SSL Verify IMAP SSL certificates (disable for self-signed) true No MCP_EMAIL_SERVER_SMTP_HOST SMTP server host; omit for read-only mode - No MCP_EMAIL_SERVER_SMTP_PORT SMTP server port 465 No MCP_EMAIL_SERVER_SMTP_SSL Enable SMTP SSL true No MCP_EMAIL_SERVER_SMTP_START_SSL Enable STARTTLS false No MCP_EMAIL_SERVER_SMTP_VERIFY_SSL Verify SSL certificates (disable for self-signed) true No MCP_EMAIL_SERVER_ENABLE_ATTACHMENT_DOWNLOAD Enable attachment download false No MCP_EMAIL_SERVER_SAVE_TO_SENT Save sent emails to IMAP Sent folder true No MCP_EMAIL_SERVER_SENT_FOLDER_NAME Custom Sent folder name (auto-detect if not set) - No MCP_EMAIL_SERVER_ALLOWED_RECIPIENTS Recipient allowlist (comma-separated); empty = all - No MCP_EMAIL_SERVER_ALLOWED_SENDERS Sender allowlist (comma-separated globs); empty = all - No

Read-only IMAP mode

SMTP configuration is optional. When MCP_EMAIL_SERVER_SMTP_HOST is omitted, the account runs in read-only mode and exposes only read/mailbox-management tools. Outbound compose tools such as send_email and save_to_mailbox are hidden when every configured email account is read-only.

{
 "mcpServers": {
 "zerolib-email": {
 "command": "uvx",
 "args": ["mcp-email-server@latest", "stdio"],
 "env": {
 "MCP_EMAIL_SERVER_EMAIL_ADDRESS": "[email protected]",
 "MCP_EMAIL_SERVER_PASSWORD": "your_password",
 "MCP_EMAIL_SERVER_IMAP_HOST": "imap.gmail.com"
 }
 }
 }
}

HTTP Transport Security

HTTP transports (sse and streamable-http) validate request Host and Origin headers to protect against DNS rebinding attacks. Localhost is allowed by default. For Docker networks or reverse proxies, configure the expected service names explicitly.

Variable Description Default MCP_HOST HTTP bind host for streamable-http localhost MCP_PORT HTTP bind port for streamable-http 9557 MCP_ALLOWED_HOSTS Comma-separated allowed Host values. Supports host:* ports Localhost hosts MCP_ALLOWED_ORIGINS Comma-separated allowed Origin values. Supports host:* ports Localhost origins MCP_ENABLE_DNS_REBINDING_PROTECTION Enable DNS rebinding protection true

Docker Compose example:

services:
 mcp-email-server:
 image: ghcr.io/ai-zerolab/mcp-email-server:latest
 command: ["streamable-http"]
 environment:
 MCP_HOST: 0.0.0.0
 MCP_PORT: 9557
 MCP_ALLOWED_HOSTS: mcp-email-server:*,localhost:*,127.0.0.1:*
 MCP_ALLOWED_ORIGINS: http://mcp-email-server:*,http://localhost:*,http://127.0.0.1:*

Bare host entries such as MCP_ALLOWED_HOSTS=mcp-email-server also allow any port on that host. MCP_ENABLE_DNS_REBINDING_PROTECTION=false, MCP_ALLOWED_HOSTS=*, or MCP_ALLOWED_ORIGINS=* disables Host and Origin validation entirely. Use those options only in isolated local development environments.

IPv6 literals in allowlists should use bracketed notation, such as [::1]:* and http://[::1]:*.

Enabling Attachment Downloads

By default, downloading email attachments is disabled for security reasons. To enable this feature, you can either:

Option 1: Environment Variable

{
 "mcpServers": {
 "zerolib-email": {
 "command": "uvx",
 "args": ["mcp-email-server@latest", "stdio"],
 "env": {
 "MCP_EMAIL_SERVER_ENABLE_ATTACHMENT_DOWNLOAD": "true"
 }
 }
 }
}

Option 2: TOML Configuration

Add enable_attachment_download = true to your TOML configuration file (~/.config/zerolib/mcp_email_server/config.toml):

enable_attachment_download = true

[[emails]]
# ... your email configuration

Once enabled, you can use the download_attachment tool to save email attachments to a specified path.

Saving Sent Emails to IMAP Sent Folder

By default, sent emails are automatically saved to your IMAP Sent folder. This ensures that emails sent via the MCP server appear in your email client (Thunderbird, webmail, etc.).

The server auto-detects common Sent folder names: Sent, INBOX.Sent, Sent Items, Sent Mail, [Gmail]/Sent Mail.

To specify a custom Sent folder name (useful for providers with non-standard folder names):

Option 1: Environment Variable

{
 "mcpServers": {
 "zerolib-email": {
 "command": "uvx",
 "args": ["mcp-email-server@latest", "stdio"],
 "env": {
 "MCP_EMAIL_SERVER_SENT_FOLDER_NAME": "INBOX.Sent"
 }
 }
 }
}

Option 2: TOML Configuration

[[emails]]
account_name = "work"
save_to_sent = true
sent_folder_name = "INBOX.Sent"
# ... rest of your email configuration

To disable saving to Sent folder, set MCP_EMAIL_SERVER_SAVE_TO_SENT=false or save_to_sent = false in your TOML config.

Restricting Recipients (Allowlist)

By default the server can send to any address. Set allowed_recipients to restrict both send_email and save_to_mailbox to a trusted set. Leave it empty (the default) to allow all.

allowed_recipients = ["[email protected]", "[email protected]"]

Or via environment variable (comma-separated):

MCP_EMAIL_SERVER_ALLOWED_RECIPIENTS="[email protected],[email protected]"

When configured, any To/CC/BCC address not on the list is rejected with a clear error. Matching is case-insensitive and understands the Name < [email protected] > form. The list_allowed_recipients tool appears only when an allowlist is configured, so default installs keep a minimal tool surface.

Filtering Incoming Mail (Sender Allowlist)

By default all senders are visible. Set allowed_senders to show mail only from trusted senders. Patterns support globs (e.g. *@company.com) and exact addresses, matched case-insensitively. Leave it empty (the default) to show everything.

allowed_senders = ["*@company.com", "[email protected]"]

Or via environment variable (comma-separated):

MCP_EMAIL_SERVER_ALLOWED_SENDERS="*@company.com,[email protected]"

When configured, filtering is applied in the read path: list_emails_metadata excludes non-allowed senders before pagination, so total and page sizes reflect only allowed mail; get_emails_content and download_attachment check the sender before reading a message, so a non-allowed message's body and attachments are never fetched or marked read, and it is reported as inaccessible — indistinguishable from a missing message. The list_allowed_senders tool appears only when an allowlist is configured.

Scope: the allowlist protects read paths only (list_emails_metadata, get_emails_content, download_attachment). UID-based mutation tools (delete_emails, mark_emails_as_read, move_emails, archive_emails) are not yet filtered and can still act on any UID; enforcing the allowlist on those is planned as a follow-up.

Note: matching is against the message's From header — local filtering only, not sender authentication. A spoofed From will pass the allowlist, so this is not a substitute for provider-side SPF / DKIM / DMARC enforcement.

Self-Signed Certificates and IMAP STARTTLS (e.g., ProtonMail Bridge)

Local mail bridges such as ProtonMail Bridge commonly use STARTTLS with self-signed certificates. Configure IMAP with plaintext connect plus STARTTLS upgrade, and disable certificate verification for the local bridge certificate:

{
 "mcpServers": {
 "zerolib-email": {
 "command": "uvx",
 "args": ["mcp-email-server@latest", "stdio"],
 "env": {
 "MCP_EMAIL_SERVER_IMAP_HOST": "127.0.0.1",
 "MCP_EMAIL_SERVER_IMAP_PORT": "1143",
 "MCP_EMAIL_SERVER_IMAP_SSL": "false",
 "MCP_EMAIL_SERVER_IMAP_START_SSL": "true",
 "MCP_EMAIL_SERVER_IMAP_VERIFY_SSL": "false",
 "MCP_EMAIL_SERVER_SMTP_VERIFY_SSL": "false"
 }
 }
 }
}

Or in TOML configuration:

[[emails]]
account_name = "protonmail"
# ... other settings ...

[emails.incoming]
host = "127.0.0.1"
port = 1143
use_ssl = false
start_ssl = true
verify_ssl = false

[emails.outgoing]
verify_ssl = false

For separate IMAP/SMTP credentials, you can also use:

• MCP_EMAIL_SERVER_IMAP_USER_NAME / MCP_EMAIL_SERVER_IMAP_PASSWORD

• MCP_EMAIL_SERVER_SMTP_USER_NAME / MCP_EMAIL_SERVER_SMTP_PASSWORD

Then you can try it in Claude Desktop. If you want to intergrate it with other mcp client, run $which mcp-email-server for the path and configure it in your client like:

{
 "mcpServers": {
 "zerolib-email": {
 "command": "{{ ENTRYPOINT }}",
 "args": ["stdio"]
 }
 }
}

If docker is avaliable, you can try use docker image, but you may need to config it in your client using tools via MCP. The default config path is ~/.config/zerolib/mcp_email_server/config.toml

{
 "mcpServers": {
 "zerolib-email": {
 "command": "docker",
 "args": ["run", "-it", "ghcr.io/ai-zerolab/mcp-email-server:latest"]
 }
 }
}

Installing via Smithery

To install Email Server for Claude Desktop automatically via Smithery:

npx -y @smithery/cli install @ai-zerolab/mcp-email-server --client claude

Usage

Replying to Emails

To reply to an email with proper threading (so it appears in the same conversation in email clients):

• First, fetch the original email to get its message_id:

emails = await get_emails_content(account_name="work", email_ids=["123"])
original = emails.emails[0]

• Send your reply using in_reply_to and references:

await send_email(
 account_name="work",
 recipients=[original.sender],
 subject=f"Re: {original.subject}",
 body="Thank you for your email...",
 in_reply_to=original.message_id,
 references=original.message_id,
)

The in_reply_to parameter sets the In-Reply-To header, and references sets the References header. Both are used by email clients to thread conversations properly.