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Documentation Index

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​
Constructor

Create a new SMTP server instance. 
import { SMTPServer } from "bun-smtp";

const server = new SMTPServer(options);
​
options
SMTPServerOptions
Configuration options for the server. See Configuration for all available options.

​
Methods

​
listen()

Start the SMTP server and bind to a port. 
server.listen(2525);
Parameters:
​
port
number
Port number to bind to
​
hostname
string
default:"0.0.0.0"
Hostname or IP address to bind to
​
callback
() => void
Function called when the server starts listening
Returns: this (for chaining)
The listening event is emitted after the server successfully binds to the port.

​
close()

Gracefully shut down the server. Active connections are allowed to finish within the closeTimeout period. 
server.close(() => {
  console.log("Server has shut down");
});
​
callback
() => void
Function called when the server has fully closed
Returns: this (for chaining)
Connections still active after closeTimeout milliseconds are forcibly terminated.

​
updateSecureContext()

Hot-reload TLS certificates without restarting the server. New connections will use the updated certificates. 
server.updateSecureContext({
  key: await Bun.file("new-key.pem").text(),
  cert: await Bun.file("new-cert.pem").text()
});
​
options
object
required

​
Event Methods

​
on()

Register an event listener. 
server.on("error", (err) => {
  console.error("Server error:", err);
});
​
event
string
required
Event name. See Events for available events.
​
listener
function
required
Callback function to invoke when the event is emitted
Returns: this (for chaining)

​
once()

Register a one-time event listener that is automatically removed after firing once. 
server.once("listening", () => {
  console.log("Server started for the first time");
});
​
event
string
required
Event name
​
listener
function
required
Callback function to invoke once
Returns: this (for chaining)

​
off()

Remove an event listener. 
const errorHandler = (err) => console.error(err);
server.on("error", errorHandler);
// Later...
server.off("error", errorHandler);
​
event
string
required
Event name
​
listener
function
required
The exact listener function to remove
Returns: this (for chaining)

​
Properties

​
options
SMTPServerOptions
The resolved configuration options (defaults merged with constructor options)
​
connections
Set<ConnectionContext>
Set of currently active connections
​
closing
boolean
Whether the server is in the process of shutting down

​
Example

import { SMTPServer } from "bun-smtp";

const server = new SMTPServer({
  secure: false,
  authOptional: true,
  onData(stream, session, callback) {
    console.log(`Message from ${session.envelope.mailFrom.address}`);
    stream.pipeTo(new WritableStream()).then(
      () => callback(null),
      (err) => callback(err)
    );
  }
});

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

server.listen(2525, () => {
  console.log("SMTP Server listening on port 2525");
});

// Graceful shutdown
process.on("SIGTERM", () => {
  server.close(() => {
    console.log("Server closed");
    process.exit(0);
  });
});