Unix domain sockets

Mailpit traditionally listens on designated network interfaces and ports for both the web UI/API (HTTP server) and mail (SMTP server). This means that the ports must be available in order to start Mailpit, which can be inconvenient when running dozens of Mailpit instances on the same server. In such situations, it may be more convenient to listen on Unix sockets instead, especially when using a proxy server.

Mailpit can be configured to listen via a Unix domain socket for both the HTTP and SMTP servers.

The syntax to listen on a Unix socket instead of an <ip>:<port> is unix:<path>:<permissions>, where:

• <path> is the path to the socket file, e.g., /var/run/mailpit/http.sock
• <permissions> is the Unix permissions to assign to the socket, such as 600

Socket files are created with the same ownership as the process starting Mailpit, and the permissions must allow read and write access to whatever process will be reading from that socket (e.g., Nginx proxy). The folder where the socket will be written must also have read, write, and execute permissions by the user starting the Mailpit service, and read and execute permissions by the service that will be connecting to the socket.

The HTTP and SMTP services cannot share a socket, and every Mailpit instance must use its own sockets. Mailpit’s Unix domain sockets do not support TLS encryption (if you require HTTPS, add that to your proxy).

Example:

mailpit --listen unix:/var/run/mailpit/http.sock:666 --smtp unix:/var/run/mailpit/smtp.sock:666

This will allow global read and write access to both /var/run/mailpit/http.sock and /var/run/mailpit/smtp.sock sockets, provided the process also has read/execute access to /var/run/mailpit/.

Reverse web proxy using a Unix socket

Unix sockets are not connectable over a network, so a proxy is required to communicate with the socket.

Nginx

server {
    listen       80;
    server_name  localhost;

    location / {
        proxy_pass http://unix:/var/run/mailpit/http.sock;

        # enable the websocket
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
    }
}

Apache

Apache support for reverse websocket connections to Unix sockets requires version >= 2.4.47 and the proxy and proxy_http modules must be enabled.

Also note the syntax should always include a |http://<anything> (even though it is completely unused!), and include upgrade=websocket to support websockets (web UI).

<VirtualHost *:80>
    ServerName localhost

    ProxyPass "/" "unix:/var/run/mailpit/http.sock|http://ignore.this/" upgrade=websocket
</VirtualHost>

Sending mail via a Unix socket

To do this, you will need to use Mailpit’s sendmail (which supports Unix domain sockets). The SMTP socket should be set as the SMTP server address with -S unix:<path> or by setting the global environment variable MP_SENDMAIL_SMTP_ADDR=unix:<path>.

For example:

mailpit sendmail -S unix:/var/run/mailpit/smtp.sock < message

If using something like the Symfony mailer, you can configure your mailer as follows:

MAILER_DSN="sendmail://default?command=mailpit%20sendmail%20-S%20unix:/var/run/mailpit/smtp.sock%20-bs"

Edit this page