Events

SMTPServer is an event emitter. Use server.on(), server.once(), and server.off() to manage listeners.

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listening

Emitted when the server has bound to a port and is ready to accept connections.

server.on("listening", () => {
  console.log("Server is ready");
});

await server.listen(2525);

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close

Emitted when the server has fully shut down — all connections have closed and the port has been released.

server.on("close", () => {
  console.log("Server stopped");
});

server.close();

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error

Emitted on server-level errors (e.g. port already in use, TLS failures). Always attach an error listener to prevent unhandled rejection crashes.

server.on("error", (err) => {
  console.error("SMTP server error:", err);
});

The error object may include:

• err.responseCode — SMTP status code
• err.code — error code string
• err.meta — additional context

---

connect

Emitted when a new client connection is accepted (after onConnect succeeds).

server.on("connect", (info) => {
  console.log(`New connection from ${info.remoteAddress}:${info.remotePort}`);
});

The info object (ConnectionInfo):

Field	Type	Description
id	string	Unique connection identifier
localAddress	string	Server IP
localPort	number	Server port
remoteAddress	string	Client IP
remotePort	number	Client port
clientHostname	string	Reverse-DNS hostname of the client
hostNameAppearsAs	string	Hostname from HELO/EHLO (populated after the opening command)